wow, You've been lurking for a long time. Welcome to TE and we wish you'd tell us about yourself in the "getting to know you" place.

As long as any bike you own works and you're happy with it, you will probably keep that bike. But some of us get bike lust and buy new ones whether we need them or not. Others of us make the leap and buy a new bike and then grow tremendously in strength with the new bike and end up riding 100 mile rides and stuff. Some bikes are so heavy, or broken, or rusty that they make riding no fun. Those are the owners who buy a new bike and then just do amazing things because now THEY CAN.
It depends. But you don't HAVE to have a cool bike, it's just fun to.

I hope that helps.