I used to keep my lenses in a LONG time, until I developed sores on the insides of my eyelids. Suckage. Now I don't even wear the contacts full time, I make sure to take breaks and go back to glasses for a while. I still sleep in them a lot, though. I don't have any vessels in my corneas, but they sure do get irritated after a while.
And yes, nothing beats a fresh pair of contacts. Especially after letting your eyeballs rest for a month or so with glasses.