Surprisingly, the magnet holds its position very well. I've had to adjust it maybe once or twice over the dozen times I've used this band. I was definitely worried when I first got it!
So I've had my Black Milanese band for roughly 2 months now.
Only had 1 issue with it. if you look at the magnet, there is a thin metal piece covering it. Mine came off.. I was at my sister's house and she had some Loctite super glue handy so I figured it's better than nothing and placed a drop or two on the magnet and put the cover back on. The intent was to be a temp fix till I could get home, but it's still holding strong.
As for the magnet itself holding the strap on. It's still strong... I don't find myself adjusting the strap very often. When I do adjust it, it's mainly due to me catching the strap on my clothes or something else and it's come a little loose.
I've read reviews etc where the band starts to lose the paint as well, mine you can't tell anything is coming off, unless you really look hard at it. And only then can you see a tiny bit fading away right where the magnet touches.
I'm not a guy who needs a band for every occasion. Have not taken the Milanese loop off since I got it.. and only looking at getting a decent priced good quality metal link style band as another option. Don't like leather on my wrist, don't care for cloth/webbing stuff, hate the silicone and plastic crap.. only watch bands i've ever liked on my watches i've owned prior to the Apple Watch are metal. *Not* going to pay more for a band than I paid for the actual watch.. So the Apple band is out.