Much of this is what I'd like to figure out, too. HOW is it saved? Only through selling it?
I also don't particularly care for selling data - my time spent in those discoveries means more to me than the money, which can be made in other ways... What I discover is to satisfy my own curiosity. (I'd still like to find a previously un-connected, independent station, for example, but I don't expect there to be any.)
Lastly - switching ships should retain data. I understand that is ED's mechanic for the pruposes of selling data, but if I switch ships, then back again, both should preserve the data.
It would seem that they're trying to support an environment with SO much exploration to be done, that the 'wipe' becomes necessary to facilitate the game and intrigue about it (to form three distinct 'games' in one: trade, combat, exploration.)
See post #15 in this thread - it works like you think it should work.