Getting too high gives me the heebie-jeebies. I fly helos infrequently now, but I'm flying and towing gliders. When I get a request for a 4000' AGL tow, I feel like I'm balanced on the head of a pin up there. The funny part is that as soon as the glider cuts off, and I can get upsidedownish and split-S away, I feel better.
When I was working on my PPL in an enstrom, I did a night X-C with my instructor to Great Barrington, Mass. It's in the middle of nowhere, pretty dark, and a good little hill south of the airport. I decided I wanted plenty of altitude over the hill. So, I climbed up to 4000'. My instructor, a 4000 hour pilot & former CW2 with half of his helo time in combat, Vietnam, shines the flashlight on the altimiter and says "Holy Crap, where are you going? I've never been this high." He may have been pulling my leg, but I got the feeling he wasn't too keen on being up there.
-- IFMU