My only experience with over-feeding came when I had to take one of my females to the vet due to her having an eye infection...
The vet flushed her eye, did a fecal and basically did an overall check.
He asked me what my feeding practice to date had been like (by that point, leopard geckos were still VERY new to me, I just happened on a great deal for five of them - and only have since then been doing a lot of research).
Anyway, my feeding practice for the first few weeks of purchasing my geckos was to throw in enough crickets (about 5-6 per gecko) into their terrarium and let them feed away (this practice was performed everyday - with me removing the crickets after an hour or so). Well, Dagny is a compulsive over-eatter. Man, she will eat anything that moves and rarely stops.
When I told this to the vet, he showed me her enlarged kidney or liver (I don't remember which one) and told me to reduce her food intake. So, now I feed all of my geckos anywhere from 2-3 times a week, all they can eat in a 20-30 minute session. Also, I take them out of their terrarium to feed - that way I can monitor exactly how much they are eatting and I don't have to worry about them sucking up mouthfuls of sand when they miss (my albino, Dominique, is the WORST hunter - so feeding her in the plastic terrarium reduces the space in which she has to travel and also increases her feeding percentage to miss ratio!!!)
Anyway - I think over feeding is really more or less a per gecko basis. I have one female, Kira, who has always been a light eatter. She's just not that interested. She still weighs a good amount, looks beautiful - I just refer to her as my "dainty" gecko. Dagny, well, she's just a brute.
Feeding, in my opinion, is a watch and see thing...
My cheap ole .2
- D