I have a rule. I don't spend more than $100 on anything the same day I lay eyes on it, unless there's some special circumstances (super deal, last day, etc).

I currently only own one bike. I've been thinking about getting another one for about 3 years now. I've found several that I really like, but I can't bring myself to think that I actually need more than one bike. Need and want are two very different things.