After I made my first base --a small shack with a portal and dropped a few things near it (a base construction terminal, the power thingy that uses organics, and some wiring), I then made a second base in another system, but about twice the dimensions. Both were just wooden shacks.
I didn’t upload either one. But when the storyline told me to return to my base, I went back to the first one through the station portal. And ended up in a fallow field. That base --including the portal-- was gone, even though it had clearly showed in the station portal list and delivered me to the spot where my portal had been.
I went to the second one to move the quest along, and have been using it as the place to work on the main base-building quests (Still trying to get one of those entities to cough up the "Save Point " recipe, but still no luck ).
Did it disappear because I didn’t upload it and then made a second one which I haven’t yet uploaded?
And if I start a third base on another planet (without uploading the base I’ve put so much work into), will my second base disappear as the first one did?
Should I upload my Second base before I build my third, so I can still use it while third is under construction?
TL;DR: What does uploading a base do, for good or ill?