its all based on idividual chams, they can go thought times where they will eat very little if anything and times where they are little piggies. are you offering variuos types of feeders?
i would say as long as he looks heathly and active he is fine.
i always look for good poops i figure if hes pooping good he must be fed well enough
if you are really worried i guess you could monitor his weight to watch for losses,
My chameleon is a fatty. I cup feed him so he eats close to 12 crickets a day plus a couple of different worms for variety. Typically if he's not as hungry one day he will want the worms more and there are left over crickets in his cup.
Though he is only 4.5months old and grows at an alarming rate. When he's older I expect his appetite to decrease.