I dunno, i put it under a heat lamp to dry it quickly. It seemed pretty hard to me. Heck farmers glue tractor blocks back together with it lol. On a mating flange area with a gasket and sealant, it will probably hold up a long time.
It's lasted for 5 years on mine so far without a problem, as I really wanted to use an aluminum water neck I had that was pitted like that.
When it gets hot it just gets harder from what I have noticed, and I only use sealer with no gasket.
Gaskets eventually seep.