For my money, it’s really not worth keeping twink equipment around. Especially now with the loot fountain shrines. You’ll find plenty of stuff.
If I were going to make any exceptions (I’m not), it’d be for exceptionally good weapons for their level and things that give movespeed. But again, you will generally find plenty of things even with yellows turned off by level 15. And honestly there are so many great leveling skills that add flat damage that you really don’t need to worry about even a twink weapon.
So yeah. I keep pretty much 50+ things that look interesting and sets. And still I have a jammed-full shared stash. There is a lot of loot to be found.