I don't really know how long they ovulate for. I assume that after a certain amount of time if they don't mate or make an egg anyway,they just absorb the follicles. I would guess that geckos ovulate at least as many times as they produce egg clutches. The record for my females is 9-10 clutches, but some go more and some less.
It probly depends on the geckos health...I have two clutchmates that ovulated from 35g-44g, seven days a week.(But it is possible that they were just ALWAYS either ovulating or reabsorbing the 'ova') Also I think it;s impossible to say your gecko hasnt ov. unless you are checking her every day.