On my standard, I tried using Glissen PC (?), a POR product, about $50 a pint, supposed to be rock hard and brushable. I didn't like the way it went on, and removed it before it fully cured. So, the answer is no, I didn't use a sealer, and they look good a year later. I hit them with a little Mothers chrome and aluminum polish now and then. I just did my IS forks this winter, they came out very nice, again no sealer.
I also used the Glissen product. Same results.
However while I polished the forks I also took care of the rims at the same time and I did use the Glissen product on them. Makes for real easy cleanup and still looks good.
The rims for the most part are hidden from plain view most times.
Use mothers after polishing and you will be very pleased with all the looks that it gets!