Still planning to get a run in for this event. I ran the BBR-9 live run using The Nomad set up in "long range smuggler config" ready for Buzzard class in this event, so technically I just need to fly from Obsidian to Windt Terminal and get running. But some of those times have worried me, so I'll probably swap out modules and enter Albatross class instead! I'm not sure that I'll manage 4 hours free time before the end!
I'm really hoping that rolling back my graphics drivers further tonight will get rid of the AMD fps problems for me, otherwise I'll probably have to pull out of this one - fast SC approaches are impossible at less than 10fps, so if I can't fix it I'll just have to concentrate on BBR-9 where the bug only affects me once.
If there's a logic to it I don't know what it is. I wasn't sure if rares would respawn if I already had some in my hold, so I didn't do any breaks at stations to wait for them -- but I've heard since that you do get one more respawn, so I probably should have.
Rares spawn every 10 minutes, although you never know exactly where you are in the ten minute cycle when you first dock at a station.
Each rare has a maximum allocation, when you initially dock you get a random amount between 1 and the maximum allocation assuming that you don't already have that commodity in your hold. You can never receive more than your allotted maximum from a spawn, so for example if the max is 18t and you have 8t in your hold your next spawn will be between 1t and 10t.
The spawns seem to be affected a little by supply and demand, rather than being totally linear probabilities, so for example when you fly to one of the really remote 1,000,000ls+ outposts that supply rares, you'll generally get a really good spawn on your first visit. Whereas late-on during my Bootlegger challenge there were a few comments about consistently bad first spawns.
Due to the slow spawn refresh when rare trading (discounting this event's timeout breaks) it's normally better to hop back and forth between stations to fill up as two or three nearby stations can normally be visited before the first one's respawned.