I don't know about weight gain per-say. But I have noticed that my ball pythons shed on a regular basis, and I think that's based upon their intake.

Usually 3-4 feeds (if it's the proper size) = shed

The longest I've had one go before a shed was 6 feeds.

I had a buddy of mine tell me that it was based on the size of snake (which would determine the size food to feed) and the amount of calories the snake intakes will determine when they will shed. Don't know if this is true, but I do know that my snakes shed usually after their 4th meal... Like clockwork.

Usually grow anywhere from 35-110 grams per month. This also depends on the size of snake, and the size of food. Keep in mind that ball pythons can swallow a lot, but that doesn't mean that you should feed them A LOT. If it takes a snake longer than 15-20 minutes to consume it's food (this time shouldn't include them killing it) then it was more than likely to big. Most of my snakes eat at a 5-10 minute pace.

I've noticed that my smaller snakes gain weight at a much slower pace, and my yearling - sub-adults gain at the fastest pace, the big guys just eat, and progressively get bigger, but it's a lot less noticeable.

I'd say my little ones gain anywhere from 15-50 grams per month. And yearlings and sub-adults gain around 50-110 grams per month. Where my big guys gain maybe 35-50 grams per month.

This is a 6 day feeding schedule, and they all eat. Very rarely do I have non-eaters, but when I do its either the time of year or a gravid female.