Interesting stuff, Cavaliere. That seems like a good idea, to stretch the frenulum whenever you skin back. I used to stretch mine for a minute two whenever I peed. And I believe that this help me to lengthen it. But at one point I started to notice stretch marks, and I was afraid that I was being too aggressive with the stretching, so I stopped. Although I may re-start at some point.
Like you, I usually allow my foreskin forward when I go to sleep, even when I am in a long term retraction phase. One of the reasons why I am an intermittent retracter is that I can't seem to make up my mind if I truly want to always be retracted or not. Part of me feels like what you have achieved, with the foreskin automatically retracting when you get an erection, might be an ideal arrangement. But how to achieve that? I think probably a longer, or absent, frenulum is essential, as well as a stretched out rigid band. Mine are by no means abnormally tight, but I think I may have to work on stretching them out more, if I really want to achieve automatic retraction on erection.
I will just add, for GarethUK, who was concerned about not being able to go back to normally covered, if he wanted to, that some on this forum claim that they have achieve states where their foreskin would no longer cover the glans, or wouldn't stay in the covered position. For them this was usually desirable, so they were happy with it. However, if they had wanted to return to a normally covered condition, I think it is likely that they could have retrained their foreskin, fairly easily, to make covering the glans the default position again. So I wouldn't worry too much about this. Just play around, experiment to see what works for you, and what you like. It's unlikely that you will make truly permanent changes, unless you do anything surgical, like frenulum detachment, or circumcision.