How often they molt also seems to depend on food availability, in addition to their age.
When I started to feed mine twice a day as a juvenile, while she was in a major growth spurt she molted probably once every 14 days, sometimes a little less. She seems to have slowed down to 45-60 days now. Your's sounds pretty normal from what I've heard and seen.
Only time I'd say to worry about them molting too frequently is if you start seeing black spots on their exoskeleton and they start looking uncomfortable and "itchy" (grooming really excessively). That indicates they probably have a infection on their exoskeleton, and they'll molt really quickly as part of their immune response to try to clear the infection.