I have to admit I am guilty of this as well, but any mantained openbsd setup should have an uptime of no more than 6 months and a well maintained openbsd setup will be shorter than that as security patches are applied.

Having said that one of the things I like about openbsd is that if you want to go dark and have an ultra stable system(no updates ever) all the pieces are there for you, (you will want to have the source, I would also make sure I have the ports tree for that release and a copy of the ports dist files.)