the portal panties don't last long just a bit like few hours, in game time, and once you're done if you accept the panties you can buy more and force it on others and fuck them when ever you want though they won't be able to fuck or be fucked by anyone else unless you have the option to keep the dick out then they can fuck you can also make them fuck themselves
if you don't accept the panties you won't really miss out on much you just can't buy the panties or the portal fleshlight which you can give to some of the "love interests" if thats what you would call it
with the panties you can also fuck yourself literally