It's when you starting treating it as "just a job" is when it becomes that. Luckily I have a job I can really have fun with and I'm doing something different every time I fly. Yesterday it was a Factory-new Matrix picked up from Piper, today it's a crappy old seneca(ok, so today kinda sucks) in Charlotte. Maybe tomorrow I'll get a TBM/Meridian flight in if something comes up. But regardless, even when I flew 135 in C310's, I always found ways to challenge myself and have fun!!!

If you're going to be a professional pilot you already know the answer to your question. ( or should) Many years ago I did the same thing only with a cessna 402. Many hours of flying right seat; great experience; no pay; and no hours logged in book.