I use araldite 2 part epoxy adhesive (super strength 24 hr cure).
I was told if you used 5 minute it would make it easier to heat up and remove the handle, if you wanted to shorten your paddle.
The last time I had a handle attached in the store the young lad mixed up 5 minute epoxy on the shaft. My first session lasted 2 waves before the handle twisted off, quickly followed by much swearing as it was a cracker day. The adhesive had plenty of time to cure.
I dried it all out, cleaned it up, and when I'd finished gluing it back together made sure there was a good bead around the join too.
I have found too that during the curing process the two parts may want to push each other apart as well, so taping them together can help.
The paddle is still going strong, and has never leaked or looked like coming apart.

