I was an avid non-washer until experts like Kenji [1] started weighing in. You definitely have to hold off washing them until the last moment to avoid sliminess. Although I don't find the time added to be all that consequential in the grand scheme of things. Obviously you're correct that it'd be *more* time, however.

[1] https://www.seriouseats.com/how-to-clean-and-chop-mushrooms