Tree protectors? most are photodegradable, so you stack em in sunlight and they fall apart over time.
in general you plant young tree's with protectors in area's where rabbits are known. they LOVE young tree's, haven't seen a protector yet that stops deer though and they don't half destroy tree's especially muntjack.
as for removal its a 9 year cycle, once the tree is about 9 years old (dependant on tree) you can remove them and stack them the tree is old enough to not be bothered by the odd nibble and the rabbits go off em by then.
most are degradable (to sunlight) some aren't and are handed about various communities like volunteer groups and the woodland trust etc to re-use through various contacts. or at least thats my experience with em

hope that helps a bit

pete