Is it permissible to spread out the Adhkar that are to be recited a certain number of times within the timeframe prescribed?
Question

Is it valid to spread out Adhkar in general, and the dhikr “Laa ilaaha ill-Allaah wahdahu laa shareeka lah, lahu’l-mulk wa lahu’l-hamd wa huwa ‘ala kulli shay’in qadeer (there is no god worthy of worship except Allah alone, with no partner or associate. His is the Dominion and to Him be praise, and He is able to do all things)” in particular? What I mean is: will the person be rewarded as mentioned in the hadith of Abu Hurayrah (may Allah be pleased with him), according to which the Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever says ‘Laa ilaaha ill-Allaah wahdahu laa shareeka lah, lahu’l-mulk wa lahu’l-hamd wa huwa ‘ala kulli shay’in qadeer’ one hundred times in a day, will have (a reward) equivalent to freeing ten slaves, one hundred hasanaat (good deeds) will be recorded for him and one hundred sayyi’aat (bad deeds) will be erased from him, and he will be protected from the Shaytaan for that day until evening comes. No one can do anything better than what he has done except one who does more than that” if he spreads out the dhikr throughout the day, for example saying it fifty times after Fajr and fifty times after ‘Asr, or twenty times after each of the obligatory prayers? Or must he say it consecutively in order to attain the reward? The aim is not to introduce innovation; rather it is to try to be able to recite this dhikr regularly, because what usually happens is that one of us recites it 30 times, then stops for some reason, and – subhaan Allah – he forgets to complete it. But if he sets out a consistent program for reciting this dhikr, for example 20 times after each of the obligatory prayers, knowing that it is not one of the adhkaar to be recited following  the prayer, the total will be 100 times a day. To explain further: the aim is to be consistent and continue in this manner, not just do it sometimes. And Allah is the guide to the straight path.
Praise be to Allah.Firstly:
What is called the adhkar of morning and afternoon may be done throughout the time that is allocated for any of these adhkar, which is the beginning and end of the day. It is not stipulated that one should do what many people do, of always reciting these adhkar all at once in one sitting. The best with regard to adhkar for which the reward is protection for the one who says them is to hasten to say them before other adhkar, but here we are talking about dhikr for which no particular number of repetitions is stipulated; rather they are to be said only once.
Secondly:
The numbers of times that adhkar are to be repeated is a matter of tawqeef [i.e., they can only be known through the religious texts, with no room for ijtihad], and it is not permissible for the one who wants to attain the reward for them to differ in the number of times he says them, otherwise he will be going against what is stated in the religious texts and will be deprived of the reward.
Al-Haafiz Ibn Hajar (may Allah have mercy on him) said:
It may be concluded from this that it is important to pay attention to the number of times that the text states a dhikr is to be repeated, otherwise it would be possible to suggest that another thirty-three times may be added to the dhikr.  Some of the scholars said: If a specific reward is promised for saying a dhikr a certain number of times as narrated in the reports, such as in the case of the dhikr to be recited following the obligatory prayers, but the reciter adds to the stated number, he will not attain that specific reward, because of the possibility that there is a reason behind that number of times and it has some special impact which will be lost by going beyond that number. Fath al-Baari (2/330).
The one who goes beyond that number and regards it as permissible to do more will not be deprived of reward. It may be that the one who adds more does not intend not to comply; rather his intention may simply be to recite more dhikr after complying, not to attain greater reward. This is how al-Haafiz Ibn Hajar interpreted the words of his shaykh al-‘Iraaqi in the words noted above.
Thirdly:
With regard to the question, it may be noted with regard to what has been narrated concerning the adhkar that are to be recited at the two ends of the day that these adhkar may be divided throughout the entire morning and the entire afternoon, without specifying a particular number to be recited after or before a particular action. Rather this number may be distributed throughout the entire time, according to what is easy for the individual, without adhering to a specific method. But what is best is to recite the adhkar that is to be repeated a certain number of times in full, in one sitting, for fear of forgetting or making a mistake in the number of times it is recited. But in terms of permissibility, it is permissible and it is not stipulated that the recitation be done consecutively. What we have mentioned is the apparent meaning of the following hadith:
It was narrated from Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever says ‘Subhaan Allah wa bi hamdihi (Glory and praise be to Allah)’ one hundred times in a day, his sins will be erased, even if they are like the foam of the sea.” Narrated by al-Bukhaari (6042) and Muslim (2691).
An-Nawawi (may Allah have mercy on him) said:
The general meaning of this hadith indicates that the reward mentioned will be attained by the one who says this dhikr one hundred times in a day, whether he says it consecutively or at different times, or says some of it at the beginning of the day and some of it at the end. But the best is to recite it consecutively at the beginning of the day, so that it might be a protection for him throughout his day. Sharh Muslim (17/17).
Badr ad-Deen al-‘Ayni (may Allah have mercy on him) said:
With regard to the words “in a day”, the word “day” is general in meaning, and it is not known at what time of the day that is, so it is not to be restricted to any specific time.
‘Umdat al-Qaari Sharh Saheeh al-Bukhaari (23/25).
Summary:
The best is for the one who is reciting dhikr to repeat it consecutively for the number of times mentioned. If that is not easy for him, he may recite it whenever he can, without restriction, doing such-and-such a number after every prayer, and the like. Rather whatever way is easier for him, he may do it.
And Allah knows best.