Since this is not a QA site as such, I don't think there's a whole lot of value in keeping old solutions around for future reference. And for new users to the site, it's a bit like discovering an awesome puzzle book, only to find that somebody has already filled in 90% of the answers. From that point of view, removing old answers should really be considered a good thing.
That said, I'm not suggesting we necessarily encourage people to do this, but if someone did want to delete their old answers, would that be a acceptable? Or are moderators likely to see this as vandalism and revert the deleted posts?