I became impatient waiting on an email reply, from Ravin, so I just called them and talked to a guy in tech support.
His advice was to lubricate the strings and cables, any day that I hunt with it and the temperatures are below freezing. Otherwise, replace the strings and cables every 400 shots or 2 years, whichever comes first. As for the 600 grain arrows, he was not in favor of that idea. They're coming out with a 500 grain arrow, this Spring and it would be fine to use those. However, he said the speed would drop from 400 to 375.
I felt better after actually talking with a Ravin employee, rather than buying into what I've been reading on other websites.
I'll keep using it as recommended and be happy.
Bowhunter57