I've been reading a lot lately about how age matters when it comes to high search engine rankings.  For example, you'll have a hard time finding a domain less than one year old in the top ten at Google.  This is bad news for brand new sites that are better, or even MUCH better, than any existing site because they will not get the rankings they deserve. 

This forces you to think as far forward into the future as possible, register all the domains you see yourself using for business, and then slapping up some content and getting a few links so that the "clock starts ticking."  By the time you get around to needing them, they will have been "pre-aged" and closer to ranking well. 

Another factor to consider is the length of the registration period for your domain -- longer is better in the eyes of the search engines, so cough up for that five or ten year initial registration period instead of the usual one year.  Will this help your rankings?  Who knows ... but it makes sense that the search engines would consider this as one of their ranking factors.  It would seem that the 10-year buyer is more serious about building a business than a 1-year buyer ...