I would like to perform Aayush Homam for my mother weho is 61 years old. Should it be done only in Janmanakshathiram ?

Answer: Ayush Homam can be performed only on the birth nakshatra day but in any month. But for Sashti Abtha Poorthy (i.e. completion of sixty full years) to be performed after the 60 years conpletion but on any of the following months on the birth nakshatra day. You can get details of the same a this page explaining about Ayush Homam.