Let's see:
Patent number: 5482209
Filing date: Jun 1, 1994
Issue date: Jan 9, 1996

So patents filed before June 2005 the patent term is the longer of 20 years from the filing date or 17 years from the issue date. Check.
Expiration is Jan 9, 2014, based on 20 years from the filing date.

Let the Lawsuit drag on for two years until the patent expires, so as long as they don't get an injunction they will just pay some damages and presumably be on their way.

Without a continuously active protection mechanism excess energy will destroy the light harvesting molecules due to photo-oxidative damage. So you might have to continually repaint your roof which could get quite expensive and be labor intensive.

Maybe it is phased or ignored out because the majority of today's commercial butter does not usually come from grass fed cows... corn fed cows produce white butter.