I can't argue with Foostrap. A few things, from my experience, matchin box fans go a very long time on lasers less than 4kw. I have problems with them so infrequently that I cannot even recommend a replacement interval. But I agree fully with the fan statement on the 4kw. There are four fans on that machine and probably 2 on the 2.5. They are about $100 each.
Big fan of discharge tube cleaning. I think for the 1.5, 2, 2.5 and 3kw machines 36,000 hours is way over kill. Maybe at 50k hours but that depends on their condition. I may be wrong, but I think the 2.5 has 4 discharge tubes. Each one cost$1200 USD.
To answer your second question. All new lasers have a one year warranty. Tubes are either 30 or 90 days. I think its the same for the power supplies.
Foostrap is right Fanuc's new power supplies are quite bullet proof. In 10 years of working on E type laser, I can only think of one failure. Not common at all.