More sex or large toys will cause, over a long period of time with much use, the vagina to loosen, just like giving brith will do it.
The same thing can happen to the anus with anal sex.
This is the reason that some women buy tightening creams, or even have an operation that "re-virginizes" them by tightening the vagina.
Yes, more sex makes you looser. it doesn't make you tighter. Your vagina is like a rubber band: it will snap back to tight, but if you over use it or force something very large through it, you weaken the stretchiness and it looses the tightness.