That’s entirely dependent on the program they’re integrated into. I personally regulate volume the same way I do for all other work, by doing what I can, when I can and watching my system to see how it responds. If my abs and/or hip flexors are still sore too long after a session or if my performance has dropped and the above exercises can be identified as the culprit then I’ll reduce volume over the next session.
For everyone else, I’d recommend they do the same. A good starting point however, might be just reducing their low intensity ab volume a bit and throwing a few sets of weighted movements into their weight sessions. Adjust volume up or down as necessary. And as is the case, it’s always better to do too little than to do too much.