I would personally be opposed to trying to suppress nocturnal erections. It’s pretty well accepted by most experts that these are designed to keep penile tissues ‘nourished’ by periodically flooding them with blood, which is what happens during an errction. Without this, these tissues can start to degenerate over time, lose elasticity due to fibrosis & over time that could result in loss of erectile function - in other words, ED !! I’m pretty sure you don’t want that!
I’m also opposed to the practice of trying to rely on wet dreams for release - there are several studies showing that frequent ejaculation clears the prostate & associated glands of fluids that can become ‘stale’ & there’s strong evidence this may help prevent development of prostate cancer. Studies showed that men who had more frequent ejaculations had a lower rate of prostate cancer later on.
As for the sleep angle, it prbly isn’t doing too much harm, but I would not continue to do this for the 2 VERY big reasons I mentioned - Possible ED & Prostate cancer.
FYI - I am a prostate cancer patient myself, so I know quite a bit about this subject - what factors can increase the odds of getting it, the purpose of nocturnal erections, frequency of ejaculation, etc., having done quite a bit of research into these topics...
BonzoDog brings up excellent points that have a medical basis. I am physician who just happens to have been locked in chastity since 1/1/2015 nearly 99% of the time. Penile atrophy happens if you stay in chastity like I have. If you are let out frequently and allowed to have erections then it isn't a problem. But if you are kept locked - penile atrophy occurs.
As far as prostate cancer goes, diet is one of the factors to consider. In chastity full time? Then pay attention to your diet.
auntiejessie is correct - pay attention to the evidence and make informed decisions.
Boy, am I confused. I can't be healthy in any way to keep any body part locked up. Not your fingers. Not your toes. I'm not sure what the device has to do with chastity, as that can be done by not having sex. Monks do it. Lots of people do it for lots of reasons. Some people just never meet anyone. Also, men don't all have nocturnal erections. Some do, some don't. I've started to recently because of a prostate problem that affected a nerve in my bladder, and that causes me to have a lot of irritation after urination that when I'm sleeping seems to be causing erections that are a total nuisance as they just make me have to get up and urinate. I stopped getting them years and years ago. Also, wet dreams are almost completely a feature of youth and then most of us just don't get them anymore as we're busy having actual sex. I haven't had one since I was a teenager. There are theories about ejaculation, I get that. Taoists believe they deplete male energy and should only be had when one wishes to conceive. It's a thing. But that does not require a device, in fact, to the contrary, the whole point is self control. It's not something I believe in but if you do I'm just really curious, why a device that again can't be good. Would you think wearing handcuffs for long periods of time are good for you because you believe the hands are the devil's workshop? Bodies are meant to be as free from constraint as possible so everything relaxes and flows as it's supposed to biologically. Obviously, our cerebrums have caused humans to behave far from biologically, but strictly as to health, this just doesn't sound like it can possibly be good for anyone.
Speaking as a prostate cancer survivor I think anything that increases your chances of getting this horror are to be avoided at all cost. As to chastity as a thing I can only make assumptions on what motivates you to do this but... Surprised your concerned about shrinkage. I mean what difference will that make? And from experience if your wife girlfriend thinks this is a great idea? Or has a headache or its too late all the time.... at least ponder why. Maybe check your phone bill to see if she is talking to someone a couple hundred times a month and seriously wonder why she is suddenly "working late" a lot. If your into that? Well at least get checked for HIV / STDs frequently if your exposed to her no matter how unlikely that probably will be with that piece of plastic/metal attached to you and the control of it (and you) in her hands.