I've been using a DP-15f constantly since the early 80's. Despite seeing a lot of hours and not always in the best conditions (shared space with roommates, parties, etc.) it has held up very well. In fact, it's been entirely bulletproof.
I don't imagine that mine will be a candidate for repair once it finally fails, but I don't worry about that happening. And I wouldn't think twice about buying one in good condition if it met my needs.