Clean up of Keen supplied grids seem aggressive

I'm on Kemik doing the Mission to destroy a renegade base build up (avoid gatling turret, destroy hydrogen tanks, smelter and miner ship.

First try my ship gets shot up. I damage all the targets, then grind them down or blow them up. The mission does not complete so I limp my ship over park it on thee platform and start repairing it. The base vanishes leaving my short on spare parts to repair with. Start over.

I park my ship without getting it shot up. Do a suit only attack, disable the turret, blow up the tanks, grind down the smelter and then grind down the cockpit. Mission completes. I bring over my ship to do a major refit. The base vanishes in mid rebiuld.

Third try. Suit only attack. Disable the turret. Do the refit. Then take out the target structures in turn. Mission Success. Fly back to Dustspire.

There is a handy out post 1.5 km away. Think I need a local base, I fly over and start building a copy of the Keen Astmospheric miner. I'm in the final stages, adding an ore detector, when the outpost and the miner I have built to a functional state vanishes. My ship, parked on the platform, remains, hanging in mid air. When I jump in the cockpit, the parked status is gone but gravity has not pulled it down to a painful landing.

So, mission sites are safe until until the mission completes, or the mission is abandoned. Outposts are treated more or less like random encounters and have a time limited lifespan although structures on Verdure seem to last much longer.

Is the expectation that planetary encounters, Unknown Signals and Outposts, need to be ransacked as fast as one can get to then and that we should expect them to time out? And that the terrain will be restored to base base, i.e. before the whatever it was was placed there? If so, I suggest that this is an unfortunate design choice.

Note that I found the manufacturing Facility near Vallation station enormously useful for the bulk component missions and was seriously bummed out when it when it vanished taking my stash of ores and components that I had left in the cargo container.