When do you know to change your stans??? I've forgotten when I converted to tubeless. Don't have extreme loss in air pressure. Haven't had any issues with sidewall tears or punctures in general. Yep, tubeless conversion has been a blessing... Now just need to keep on top of maintenance...
from what i've learned, a good indicator is if when you unscrew the tip of the presta valve, and you tap the top to let some air out and if only air comes out and no STANS splooges out with the air then you are pretty dry and should probably add some splooge. i recently had to add more to my front wheel, i think i lost a bunch when my tire folded over on TRAIL X when I ate shit that day.
Yeah the valve/spray test is good and also just taking the wheel and shaking it, if you don't hear any sealant sloshing around then its all dried up and time to add more. I seem to have to add more sealant about every month and half or so.