For large warjack appendages you can pin them as well.
I have not had too much trouble with zip kicker being weak in the long run except when I either let go too soon (4-5 seconds of holding after zip kicking seems to work) or I use an inappropriately large amount of super glue.
For smaller figures I still have appendages fall off from time to time. Picking up a nice transport case helps a lot but I have more than one Nyss that needs an arm re-attached.
If you are a lunatic (me) you can pin at least some of the tiny joints but it takes a LOT of time, loads of drill bits, etc. I can't honestly recommend it, but I do have some models I did this with.