Googling around for a crystal-clear soft sealant that doesn't yellow, and Ess Flex MF-X is probably the only one I've found whose promotional text doesn't seem to hesitate. (Tec7 wrote a warning that theirs could yellow if the sun shone on it during curing.)
Ess Flex MF-X has been around for a few years, so someone should have been able to track its durability.
Ess Flex MF-X has been around for a few years, so someone should have been able to track its durability.