Walter Cohen writes:

I'm sure this has been debated before.

Yes, and the intelligent conclusion is that even if the coatings worked,
they are horrifically expensive per pound of material applied, compared to
new bulk asphalt. You're much better off saving your money and applying it
to new asphalt when that day comes. So-called "sealers" are an expensive
way to paint a few thousandths of an inch of asphalt on top of inches of
asphalt.

Now if you really, really like the look of a fresh paint job, then maybe it
is worth the money and/or back-breaking effort on that basis, but the
alleged durability claims would be a false economy, even if they weren't
dubious.

Take a look at what bulk asphalt typically costs your paving contractor:

http://www.dot.state.fl.us/Construct...t/fuel&bit.htm

Now compare that to what retailed sealers cost, which are mostly water and
clay and sand, and relatively little actual asphaltum.