I suppose it depends on your personality, perspective and how you grow your company's culture.

I just finished reading Tony Hsieh's upcoming book, Delivering Happiness. He describes how LinkExchange, his first big company, became boring to grow because the company culture wasn't fun. But he still enjoys working at Zappos because he and his execs managed to keep the company culture fun and interesting. He doesn't know everyone there, but it has a great feel to it. Keeping his employees engaged, serving his customers, etc. are all great joys to him.

Note that I'm not saying Zappos still feels like a startup. I think from the book it's apparent that it doesn't have a startup culture at all. But it does have an "engaged" culture. Everyone enjoys what they do.

Side note: I don't recommend reading the book. There are about 10 pages in it I actually felt I could generalize to be useful.