I reckon the best way to connect masts re later gaps or later sticking together is to rinse out the top half of the mast with clear water and then join it with the bottom half. Make sure to not put down either half after you rinsed them. Initially they'll want to pop apart due to the water sealing the air into the top and there being pressure if the top is sealed. One just wiggles and turns the top until most air has escaped and then slides the mast up the sleeve. Had never had a mast come apart or stick anymore after I adopted this method.
Good in theory but there are a lot of places that have no access to fresh water. I would also suggest that unless you sail at the beach getting your mast stuck together is not overly common? With this in mind, they almost always become stuck because you got rinsed during your session and sand etc was washed into the join. The only real way to avoid this is to tape the join, any amount of washing pre session will not help you.
I've never taped a join myself, mainly because i'm lazy and just want to get on the water; if my mast ever gets stuck, which is rare, I just whack a few booms on and presto :)
