>>1.past partners penis sizes>>
I think that recent activity with large instrument (dildo,penis) would temporarily stretch things out for a few hours, but would come back to original size.
>>2.quantity of past partners or amount of use in general>>
repeated use of a small instrument would not really affect size, however repeated use of a larger one could confer semi permanent size increase that might revert towards previous size during a several week period of abstinance.
3.pure genetics and age.
I think that some stretch easier than others, just like some guys are easy gainers and some are not. After menopause and with decreasing hormonal stimulation the vulva and vagina tend to atrophy (get smaller and drier) making intercourse uncomfortable if orifice is too small or lubrication is not adequate.
>>what do you think assuming the woman has never had a child.
Personally, my girl and I have talked and she’s had quite a “wild” past as have I - yet she is still quite a snug fit…….(and i’m not exactly girthy - hence my presence here).>>
In general I think that women who have never had a vaginal delivery have snugger pussies and stronger pc muscles. however a woman who is faithful with kegels can strengthen the pc and make the outer 1/3 of the vagina very snug indeed.