Depends on how big and how often she's eating and how quick she's growing. If she's eating appropriate sized meals as often as she should be, IMO probably every month to every other month is acceptable.
ok i was starting to worry i got her on august 28 and her card said she had just shed she eatss a good sized fuzzy every 5 to seven days. it seems like shes got bigger though and she hasnt shed but if two months is still ok for her age then im not so worried