Chastity play can be great fun leading up to a session or during a multi-day event like a MindFuck. I personally don't get any joy keyholding for a distance slave and I refuse these requests.

Chastity devices themselves are very problematic. As Aspx has said, they tend to slip off (causing great pain), pinch, chafe, wake you up in the middle of the night (which I actually find a plus) and cause hygiene issues.

I have two subs I play with regularly that are truly kept in long term chastity - one by his wife and the other by an online chastity Mistress. Both remove the device daily for cleaning. Both have custom devices.

The off the rack devices are seldom adequate for even short term chastity. A week is the longest I have had a sub wear one of these. Most attempts even for this short period fail due to the device falling off or causing some issue that makes removal necessary. Because of this I use the plastic numbered locks. If the sub has to remove the device he can, without disturbing Me - and there is no "taking it off for a little bit" without Me knowing.

I have the CB2000 - CB6000, a Bon4, multiple metal devices, including the birdcage. I have used the Holy Trainer, without success. Whether a device fits has a lot to do with a subs anatomy. What works for one sub, won't work for another. If you have a "turtle", forget about it. If you have a foreskin, it's probably best to forget about it. If you have huge balls, forget about it.