I also find maintaining my own code boring. In my head, I've already done all the interesting bits. Letting someone else work on it, then bring it back to me makes it interesting again, because it turns on all sorts of new ideas based on what the other person discovered (and I missed).
In general the best code I've ever been part of has included passing code around the group. Ownership of modules was shared by at least 2 people, and everyone had input on it. Unfortunately this gets ruined frequently by the type of dev that thinks my changes to his code are an insult ("it was working just fine before, now its all weird, I don't know what you did" where before means before the spec changed).