To keep deer from browse tubes would have to be no less than 6 feet and probably 7. Even with the cages deer still manage to browse some. Except for apple trees which I've never tubed, the Silkies and Hazelnuts are bush type trees. I should've never tubed them. I showed the poorest caged trees, the others are much larger since removing the tubes than these. What I do like about tubes if anything, is you easily know where trees are planted especially when done in managed fallow fields that are thick with growth.
And in fairness, may depend on how one manages. I'm the type I plant and walk away. You can see I don't mulch, seldom spray for weeds and grasses around the trees, etc. Nature doesn't do that, why should I? If a tree lives, so be it, if it doesn't , then it doesn't deserver to coexist with me. Im not babying them or anything else on the farm.