A simple goal to shoot for is 500 grams a year. This may sound like it is a little underweight for some of the numbers people throw around on the forum, but in the long run it is a pretty safe goal to reach for.
Most of my pythons do not go off feed for their first winter. The second winter always seems to be the worst. By year three they are either breeding or very close to it.
Year one = 500-700 grams
Year two = 900-1250 grams
Year three = 1300-1700 grams
This is only a loose guesstimate as far as what you can expect. Like you said yourself - there are many variables involved between your husbandry practices and the individual snake's own preferences and biology.
If you give us a few more details about your snakes we can most likely give you some feedback about how they/you are doing.
Age,
Sex,
Prey size, type and frequency