Depends on the vitamin powder. Some contain too much of certain vitamins that can
build up to toxicity levels if given in too large of amounts.
The "standard" recommendation is for calcium 5x a week and vitamin 2x a week.
I too do a mixed calcium/vitamin dust every day instead of switching back and forth,
but I keep my ratios at about 4 to 1 (4 calcium to 1 vitamin). I honestly don't know
if that's better or worse for them, but it works out best for me and they ARE healthy
with those levels of supplementation. They get regular check-ups with a reptile specialist
vet in the area to ensure that.