I did my first Savage with Rattle can Polyurethane back when it had a "Tint" to it. Yea , nice thick coats ... Three years later it started to peel .
I did my Harley tank with the newer stuff a year ago , no tinting this time , thin coats , three + hours between coats , and its still looks good (so far) .
I refinished some furniture in my kitchen one winter. A few specks of Polyurethane got on the floor. A few weeks later when I noticed it , I tried getting it up ...
... It didn't come up ...
... nothing would touch it !