There's a number of ways to stretch strings fairly quickly. I string at least one bass a week and don't have a problem getting strings to pitch and having them stay that way. Proper wrapping around the post and tuning them sharp a half step or two initially helps to tighten the wraps. By the time you get thru all four you can go back to the first one and tune it to pitch, etc. I'm a believer that the more string you wind around a post, within reason, the fewer problems you'll have with staying in tune, all other things being equal.
Think about it: Some players (especially guitards) change strings daily on tour, either they're in tune or they don't care. There must be a way for the ones who do care to be satisfied. I guess they have to go thru a lot of techs before they get one who knows how.