If one learned a masechta but never made a siyum, is it OK to make a siyum even weeks or months later, for the sake of erev Pesach (so that the firstborn can eat)? Or is there a time limit?
One should only make a siyum if he finished the mesechet etc. on erev pesach or during the nine days. ONe may learn a little bit slower in order that it comes out that he finishes at that time, but if he learned the mesechet already then it is improper to do.
Shut Mekor Chaim ( R’ Segelovitz) 36, R’ Shlomo Kluger in sefer Hachaim 551, Eliyahu Rabba 551-26, M:B 551-73, there are those who argue but see Yichave Daat 1-40, and Toras Hamoadim Bein Hamitazrim 5- 52.