Question: It is known from the gemara ([Shabbos 31a](http://hebrewbooks.org/shas.aspx?mesechta=2&daf=31&format=pdf) and cited in [maamar Toras HaBayis ch. 1](http://hebrewbooks.org/pdfpager.aspx?req=33083&st=&pgnum=5), among other places) that when a person dies, he is asked if he had set times for learning. I know that these times can be as little as possible: For example, he might learn one pasuk a day.

However, this is my question: Is it possible for his kovea itim to be *at least* one pasuk a day, or *at least* one mishnah a day, etc.? In that case, he can learn two if he wants to. Or, on the other hand, is it a "gezeiras hakasuv" that it must be the same amount every day?

As a side point, where is the requirement of kovea itim brought down in the Shulchan Aruch?

Answer: 
Shulchan Aruch OC 238:

א. צריך ליזהר בלמוד הלילה יותר מבשל יום, והמבטלו עונשו מרובה

ב. אם יש לו חק קבוע ללמוד כך וכך ליום והיה טרוד ביום ולא השלימו, ישלימנו בלילה מיד

Regarding upper limits, I believe this is a Nedarim question. The Gemara says (Nedarim 7a):

אמר רב גידל אמר רב: האומר לחבירו: "נשכים ונשנה פרק זה", עליו להשכים

Shach (YD 203:5) writes that even if one just says "I will learn x" without using the language of a neder, he is bound by these words. Moreover, if someone decides to accustom himself to doing a certain good thing and his plan is to always continue doing so, it retains the status of a neder even after one time (Shulchan Aruch YD 214:1). According to the Kitzur Shulchan Aruch (67:7) if one does it three times then it retains the status of a neder even if his plan was not specifically to always continue doing so.

All this being said, it would seem that there is no problem with specifically planning to always learn at least a mishna, or something like that. Since you have a specific plan, I would say that doing extra every now and then doesn't mean anything nedarim-wise. However, if every day you do an "extra" mishna, and you don't continually specify that you are still sticking to your original plan and this is just an exception, it could be that your "plan" doesn't help. I'm guessing here.
The Shulchan Aruch rules ([OC 155:1](http://hebrewbooks.org/pdfpager.aspx?req=49624&st=&pgnum=84))

> 
> אחר שיצא מבהכ"נ, ילך לבה"מ; ויקבע עת ללמוד, וצריך שאותו עת יהיה קבוע שלא יעבירנו אף אם הוא סבור להרויח הרבה.‏  
> 
>  After one leaves the synagogue he should go to the study hall and establish a time of study which should be fixed such that it won't be overridden even if he will gain much [money].
> 
> 
> 

The Mishna Berura there ([sk 4](http://hebrewbooks.org/pdfpager.aspx?req=49624&st=&pgnum=84)) quotes a Yerushalmi (Brachot 9:5 רב חלקיה...‏) that implies that these fixed times are meant to be minima for Torah study and that one who only learns at fixed times when he has other free time available is as if he rejects God's covenant.