I guess I don't understand. You've verified everything up to the time you exit the network. You have an up to date UTXO set and the last 2016 blocks or so. When you return, you can download all the blocks from the longest candidate chain and verify them working forward from the UTXO set , can you not?
Yes, that's fine provided there are nodes in the network that can serve you the blocks you haven't verified yourself. A brand new node of course needs to verify every transaction in every block all the way back to the genesis block (to keep the current level of security).
I'm very comfortable with that fact. There will always be enough of us that will hold copies of the full blockchain out of purity or shear paranoia.
Yes I agree. I would feel a bit better if there were an incentive to do it, but that isn't hard to imagine. Something like a small payment per block served should be enough to incentivize people to hold it (and also to share it when needed).
