Profinity is the tendency for being able to do and enjoy a thing! The thing that one has profinity for can be just about anything, so long as it is something one can actively do.
One may travel many shag miles to have sex with the right person. However, some people are either fortunate enough to have their sexual partner nearby.
Others, though, may simply be lazy or unimaginative and find or remain with their sexual partner simply because they are close to er.. hand. This is a "proximity shag" (noun and verb).
A: We split up because he is too many shag miles away. You on the other hand...