Well, no, not at all. Think about it. For argument's sake, say a spider molts after 1 week of hatching. The next molt would take 2 weeks. Then 4 weeks, and so on. After just seven molts, you're looking at ~2.5 YEARS between molts. And at nine molts, it would be ~10 years between molts.
No, the length of moult cycles varies due to a myriad of factors. While moult cycles generally get longer as the tarantula grows larger (before remaining roughly consistent as adults, say once a year for faster growing species), I have had instances where a tarantula has had an unusually short moult cycle (but these instances are extremely rare).
There are so many factors that impact molting. They do molt less often as adults because they are obviously growing less thus the need to molt is decreased. But none of mine have set predictable molting periods. Although something interesting (and maybe someone else can explain it or relate to it), mine tend to molt all/most around the same time. Pardon the crude comparison, but, its kind of like how they say women who live together's cycles match up eventually, once my Ts are established (they are housed separate but right next to each other in a line in glass enclosures), when one molts the others tend to follow suite. But I have no idea why lol
Coincidence, when you've got dozens of them you're bound to get a bunch of moults around the same time every now and again.
Coincidence. Observed this myself, for a bit, then out of sync, then back on, then off.... Coincidence.
