It would be helpful if you could say how old they are and how many clutches they've laid. I have not had this problem with leopard geckos. I find that the geckos that lay a lot (more than 10 clutches in a season) will very likely not lay that much the next season, or maybe ever. I had a female that laid 10 clutches her first season with 100% healthy hatchlings, never came near that again, and was retired in her 3rd or 4th year because she wasn't producing. On the other hand, my current champion layer produced 8 clutches last year with 100% healthy hatches and this year just laid her 11th clutch (15 healthy babies and counting). The only other problem I've had with leopard geckos is one gecko that did well her first season and then looked just terrible after laying eggs (very thin, kinked spine) the next season. Needless to say, she was immediately retired.
What I'm saying is that it's possible your girls aren't actually laying themselves to death (but more data would be helpful).
The one gecko I had that probably did lay herself to death was a SW banded gecko (Coleonyx) that laid eggs every 2 weeks for 11 months (29 healthy hatchlings), took a 6 week break and started up again. In retrospect I probably should have cooled her and that may have stopped her laying, but she looked very healthy right up to the day she died.