I didn't mean picking a system, but for example how long it takes for one faction to move from pending expansion to actual expansion that can take either shortest 5 days or longest 7 days in which time you need pay attention that the spot you created will not be taken by other factions and no, players actions are not the only thing affecting the bgs otherwise it would've been even more dead than it is. And even thou I cannot track 100% of times if a player did anything in a currently active conflict but I can assure you that rng is a huge part of this game.
Ok Expansion pending is always 5 days no if ands or buts. The active time is what's different cause Odyssey messed it up. And of course you have to watch for other factions snagging the system you want. That's why you use Inara and plan around other expanding factions.
RNG is a huge part of the game but not of the BGS. There are many systems out there that never change because no one does anything in them. How do you think people test BGS mechanics? They research systems that have zero activity then go do their testing there.