Personally, I prefer to allow websites to use those things, but to then clear them between browser sessions. Just use the Firefox BetterPrivacy addon.

I don't know how you work but I keep the browser open 12 hours a day which is a very long session. During that time they can track you across their network of sites if you allow those types of storage by default in the first place.

This is true. I do however use AdBlock, Ghostery, Flashblock and NoScript as well, which should stop the vast majority of that sort of tracking.