I have not tried mixing non-latex sealants so I have no idea whether they mix or not.
Non-latex sealants I would never mix with latex ones. When I remove the tyre to swap for something else, I take the opportunity to clean the rim and also the tyre, especially the beads.įor topping up I would use the same sealant for preference, but if it was latex I have used any latex I happened to have without a problem. That provides a useful opening to either add more sealant the quick way or to remove any latex objects rumbling about inside. I remove the wheel and pop the bead on one side enough to see what's in there. I tend to take a look inside the tyre after about six months or a few months after my first top up. I take this as a cue to either add more sealant or see what's going on. But as the punctures increase the tyres slowly need more and more air each time I ride. I check my tyre pressures before every ride and for the first month or so they hardly need topping up. I have never used it and some even jeer at it. I have seen recommendations for a dipstick inserted through the valve (core removed, valve at the bottom).
Once you run out your first puncture will become a flat. But of course every time you get a puncture or burp the tyre, you will lose some sealant, so you may run out before it goes off. Between 3-6 months seems to be the range. However you describe it, it becomes useless at moving towards a hole to seal it. By "go off" I mean sets like stringy glue, or even into a random shaped object that moves around inside the tyre. If it is a latex based sealant, you may have to top up very frequently depending upon the climate as it does dry out or "go off".