My experience with self-sealing tubes and add on tire liners, have left me with some impressions and general rules of thumb.

The air pressure you run your tires at, will have a lot to do with how well the sealant and/or liners work for you.

With the trend being that as the recommended pressure rating of the tire increases beyond the 60/70-ish psi point the less satisfactory your experience will be.

There WILL be a point where if you put in enough mileage that there will be a puncture that the sealant will not be able to cope with (again with increasing air pressure the smaller the puncture this point is reached), then you will have a mess to clean up before you can install a new tube. The punctured tube is not repairable.

Be aware that there is also a shelf life for the sealant which is reduced if the bike is not used on a regular basis (example being a three season commuter which spends the *off season* sitting around) as the sealant settles in the lowest point.