every chance all 4 could be in use when I arrive…
SatNav will show you occupancy / free stalls as you approach - if you have a choice of an alternate you could take that decision
But if all stalls are full and queuing is necessary a lot depends on the site - none of them were designed for queuing for EV chargers ...
I agree its worth having a go when not critical. My suggestions would be:
Worth sitting in the car for a minute or two and checking that it ramps up to "expected" kWs. That used to be something that was easy to know, but now there are "old" stalls and also "new" ones. I suppose a simple rule of thumb is that if the stall has two cables (one that will fit M3/MY and the other for legacy MS/MX) its an old one. A bit over 100 kWs is the limit. For that "old" type the stalls are in pairs (marked A and B - so 1A, 1B ... 2A, 2B ...) and they share power. So you should park every-other-stall to avoid sharing (the A/B are not always adjacent stalls, particularly when they go round a corner, so best to check that ...). Pairing/sharing is all the more important on these, old, stalls as they are lower power anyway.
On a new stall (one cable) you could get 200kW - maybe 250kW for brief periods. To get full power your car needs to be "low" state-of-charge - around 0%. As it fills up the kW will drop. Might be worth monitoring it (the first time) and making a note of kW at 10%, 20%, ... so you know what to expect. Also depends on the temperature of your battery and so on ...
Some sites (e.g. M4 hotel near Heathrow) have a mix of 2-cable old chargers and 1-cable new ones - definitely want to park at a new charger stall there
But basically the car should charge "fast" from 10% to, say, 60-70%, quite a bit slower up to 80%, quite a lot slower to 90%, and then VERY slow to 100%. So if you can (i.e. you can get to next charger OK) charging to 70% is probably about ideal. But (unlike brim-filling the tank in an ICE) you only need enough to get to your destination / next charger - and if that is home presumably you have cheaper fuel there than the Supercharger price.
If you get much less kW than you expect (make sure you are not sharing an old stall) then move to another stall. On fairly rare occasions a stall may be running slow ... hence my suggestion to stay in car for a minute and check it ramps up. Annoying to head to the facilities, come back 15 minutes later and find you've only gained a dribble
if there aren’t any others available as you and your partner will charge at half the rate.
its not quite like that, the car that started first gets the lions share ... but as they fill up to 70% their kW drops anyway, and then the 2nd car gets more ... and becomes the 1st car once the original car leaves.