Good morning. I've not been around this board long, but have been retracting on and off for the past 5 years of so. Right now I am starting the 2nd week of 24 hour retraction. I'm not sure there is a real pat answer to your questions. I would say, from my experience, that it takes longer than a few days to get to a more permanent state. I would also theorize that the initial loss of sensitivity you may/will experience will fade and that when you are using your tool for its intended purpose, you will have plenty of sensitivity. The sensitivity will be different.
You are the only one to know if it is successful or not. What are you going to miss out on if you give it a try for a while? My foreskin will remain back quite a bit (12-14 hours of the day) just by peeling it back, however, I added a small rubber o-ring right behind my glans this week and it has helped my foreskin to remain retracted 24 hours a day, even over night, with no issues that I've been able to find. The ring I am using I purchased at a hardware store and it is pretty elastic, so has caused no concerns with being too tight, whether flaccid or erect.
I encourage you to read the many posts on here and find a method that you are will to try and commit to. Many seem to have good success with the spoon method, so you might try that one.
As near as I can tell in my 55 years on the earth, it is highly unlikely that your foreskin will just disappear, but you may get some nice results. And the best part, despite the loss of some sensitivity in the glans, you will still have your foreskin, which is full of nerves and provides plenty of sensitivity. And, if you experience any discomfort from pulling back, just roll it forward and let things calm down for a bit and start again.
This is a marathon, not a sprint. Keep us apprised on your progress.