RE: Older Kyosho Concept
Providing everything is in good condition, go ahead and fly it. The concept helis fly fine for a beginner ship. The problem is that parts are sometimes hard to find. I wouldn't go crazy upgrading anything except maybe the gyro, but the mechanical ones work fine for basic hovering practice.
I was out flying my 15yr old concept 30 last week. It still hovers pretty solid and is really smooth in forward flight. Aerobatics are pretty much out of the question with it though.
Ben