This is an interesting question to me. I'm going to be working on my current story for a long time (it's looking like at least 10 years...), and I only have so much 'make comics' energy, so it's all going to that right now.
Energy aside, though, I deal with a lack of ideas. Well, that's not true. I deal with a lack of ideas that I can use. Part of what kept me from making my own comic for so long is that I have a tendency to love making my own OCs.... but then dump them into an existing fandom's world. So I have all of these awesome, dynamic, fun ideas for characters and stories... set in/inextricably linked to existing, copyrighted worlds.
This has been a long-term problem of mine-- I enjoy world-building, but it's daunting and exhausting, and other people are better at it. If I did another project in the future, I think I'd have to set it in a modern day setting, just so I didn't have to worry as much about the world-building.