For 28mm tires, I use 30ml of Orange regular sealant.
Depending on the season, add back 30ml after 3 or 4 months.
Checking with a 2 hex screwdriver, through the valve placed at the bottom.
Then my tires are in general worn out before a 3rd refill.
Coupled with Dynaplugs, it has been years without an unfixable flat.