How Do You Decide If You Will Renew A Domain Or Not?

I dont mean domain names where you have sites up and running, but domains that you have that are either parked somewhere like Sedo, or still at the registrars holding page.

What makes you decide to renew an as-yet unused domain name?

The reason i ask is we have about 100 domains coming up for renewal in the next week and im seriously thinking about dropping most of them except the ones that have paid for themselves in parking commissions.

I know a lot of people dont even bother parking their domains though, so what makes you decide if you will let a domain expire, or you are going to renew it?

Regards,

Lee

I never let anything go before having tried to sell it for a month or so... the unsellable ones that was purchased in the spur of the moment that hasnt paid for themselve over the year are dumped..