Hello Mackenzie, I usually wait for my plant to go dormant then I hard prune it. I like doing it while it is dormant so I can also lift the caudex, check the root area and see if I need to do some root pruning too. Then I put it back on the same container, making some improvements on the media, caudex lifted a bit higher. Just keeping it dry and warm and wait patiently for the plant to wake up again in Spring.
It is your choice up to what height you want to prune. Typically if it is growing too leggy like that, it indicates it needs more direct light access. So make sure later on, when season's go warmer, position slowly in part sun, then as temps goes higher, move into more direct sun access. Make sure your media is much more well draining and gritty so that even if you do daily watering at the peak of summer, it will not rot the roots.
Just editing to add, I do my pruning towards early Spring, so it is nearing the time for Adeniums wake up time.
