For youtube, sticking it on 'watch later' is one approach, or some other playlist. Even better, that way you can cronjob a script to save them locally. I'll leave youtube tabs for too long (despite this) and too often I've eventually returned and it's been removed. My other tab-shrinking habits are bookmark folders in the form "year-unread" and a local txt file where I loosely dump related URLs into pseudo-categories/sections.