I don't pop the bead unless I need to take the tyre off.. Over time you will get a feel for how often you need to refill - but this depends on how much cycling you do over the year (and in what conditions - visitation season is here with the rain so more likely to get incidents now which use up sealant). For me, every 2-3 months. Sloshing and weighing might work for some sealants and not for others. (Cafelatex for example foams on agitation so won't slosh except for initial filling.)
I just top up, more is better than none. If I am going to ride a long audax or tour, I just pop in another 50ml per wheel to be on the safe side.
I'm also not one for cleaning out the tyre between fill ups, all you are succeeding in there is breaking the seal its made on the rim and removing a protection layer from inside the tyre. I generally find I wear out a tyre before it becomes heavy with sealant
Whilst I carry a spare inner tube, all the times I have had to use it have been due to lack of sealant, so now I just carry a sealant top up - if you don't break the seal of your tyre, you won't have problems with it popping off and needing to be reseated in the wild

Both Schwalbe and Effetto Mariposa Caffelatex do small refill packs that can be used on the road.
It goes without saying that you should inspect your tyres for embedded flints and pick them out before they become a bigger issue
If you sdo need to take the tyre off you will save yourself a lot of faff when remounting if you ensure you clean the rim well and also the bead of the tyre, soapy water will help with seating. If you are replacing the tyre, then clean rim is where the pain is avoided.
On the road, tyre worms are you friend - there's some great practical advise from Malcolm at Cycle Clinic which is worth looking at.
https://thecycleclinic.co.uk/pages/tech-page
https://thecycleclinic.co.uk/blogs/news/living-with-tubeless-tyres
I think I must be close to 50,000km on tubeless now, unless the bike is going to be sitting in the garage for most of the time, I wouldn't go back to tubes

YMMV obvs