Before you plan on using them?

Today ive been going through our current domain portfolio checking the names i want to keep and the ones i want to let expire and i came to the conclusion that im addicted to registering domain names LOL

I have several domains that we have owned for over 5 years that have been left relatively untouched that we still plan on using 'sometime' in the future and i was wondering, how often do you register new domains and, when you do, how long in advance do you register them in comparison to how quickly you are going to end up using them?

Regards,

Lee