I let my tegu decide. He goes in spurts of growth accompanied by an increase in appatite. When he is hungry he'll eat a lot every day. This could mean half a dozen mice, or a couple of week old quail, or half pound of turkey/fruit mix. Food will be consumed like a ravenous beast.
He has just come out of one of those spurts. He will now gingerly eat a few (2-4) mice over a 20 minute period. He'll only eat every 2-3 days now. I will have to wrap up this food and put it in the fridge on the first day of reduced eating cycle. The extra food is warmed and fed out over the next several days - week.
I figure he knows more about tegus than I.
Brian