Where can I do a long retreat? Could different people here recommend places I can do long retreats (in 2 months for example)?

I wanted to do a retreat in the style of meditation I do right now: Mahasi Sayadaw following Ven. Ajhan Tong sirimangalo technique -- where you do mindful prostrations, then walking and sitting while using labeling.

But they only agree for 10 days, and at the end of 10 days they tell you whether you can stay for another 10 days.

So I'm looking for a place to go do a long retreat, of say 2 months -- it can be in different technique even  (say even only metta for example) , that isn't close to it.
You can try the Kanduboda Meditation Center which teachers Mahasi Meditation. You have to inquire before hand about the length of your stay.

Also you can try Mitirigala Nissarana Vanaya. Again double check the particular days. This teachers both Mahasi and Pa Auk methods under Most Venerable UdaEriyagama Dhammajiva Maha Thero

Also there are centres in Sri Lanka, Burma, Thai Land and Malaysia which you can try.

Also see: Meditation Centres in Sri Lanka by Andrew Quernmore

Also you might try to use World Buddhist Directory.

Also Goenka Centres does have long retreats if you fulfill some conditions: 


  10-day Courses for Old Students have the same timetable and discipline as 10-day courses. These courses are open to serious old students who have completed at least three 10-day courses and one Satipaṭṭhāna Sutta course, have not been practising any other meditation techniques since last 10-day course, have been practising this technique of Vipassana for at least one year, are trying to maintain the five precepts in their daily lives, and trying to maintain daily practice.
  
  Special 10-day Courses are open only to serious Old Students committed to this technique who have completed a minimum of five 10-day courses, one Satipatthana Sutta course, given Dhamma Service at least one 10-day course, and have been practicing regularly for at least two years.
  
  Applications must be submitted well in advance as processing may take some time. Students who speak neither English nor one of the other announced course languages may apply for the course, however acceptance into the course will depend on the availability of required course materials, suitable translators and permission of the teacher conducting the course.
  
  20-day Courses are open only to serious Old Students committed to this technique who have completed a minimum of five 10-day courses , one Satipatthana Sutta course, given Dhamma Service at least one 10-day course, and have been practicing regularly for at least two years.
  
  Applications must be submitted well in advance as processing may take some time. Students who speak neither English nor one of the other announced course languages may apply for the course, however acceptance into the course will depend on the availability of required course materials, suitable translators and permission of the teacher conducting the course.
  
  30-day Courses are open only to serious Old Students committed to this technique who have completed a minimum of six 10-day courses (one since their first 20-day course), one 20-day course, one Satipatthana Sutta course, and have been practicing regularly for at least two years.
  
  Applications must be submitted well in advance as processing may take some time. Students who speak neither English nor one of the other announced course languages may apply for the course, however acceptance into the course will depend on the availability of required course materials, suitable translators and permission of the teacher conducting the course.
  
  45-day Courses are open only to persons involved in Dhamma Service and Assistant Teachers who have completed a minimum of seven 10-day courses (one since their first 30-day course), two 30-day courses, one Satipatthana Sutta course, and have been practicing regularly for at least three years.
  
  Applications must be submitted well in advance as processing may take some time. Students who speak neither English nor one of the other announced course languages may apply for the course, however acceptance into the course will depend on the availability of required course materials, suitable translators and permission of the teacher conducting the course.
  
  60-day Courses are open only to active Teachers and Assistant teachers who have completed two 45 Day courses and conduct at least 4 courses annually.
  
  Applications must be submitted well in advance as processing may take some time. Students who speak neither English nor one of the other announced course languages may apply for the course, however acceptance into the course will depend on the availability of required course materials, suitable translators and permission of the teacher conducting the course.
  
  Satipatthana Sutta Courses have the same timetable and discipline as 10-day courses. The difference is that in the taped evening discourses the Satipatthana Sutta is carefully examined. This is the principal text in which the technique of Vipassana is systematically explained. These courses are open to serious old students who have sat (not including courses served) at least three 10-day courses, have not been practising any other meditation techniques since last 10-day course, have been practising this technique of Vipassana for at least one year, and who are trying to maintain their meditation practice and the five precepts in their daily lives, at the very minimum from the time of applying to the course.
  
  Old Student Short Courses (1-3 days) are for any student who has completed the 10-day course with S.N. Goenka and his assistant teachers. All old students are welcome to apply to attend these courses, including those where it has been some time since their last course.


Source: https://www.dhamma.org/en/schedules/schtapovana