Its EZAir's common since that if a customer would buy the largest unit with a 20 year warranty, for these reasons.
These EZAir units are made to last for a long time running 7 days a week 24 hours a day. You should not have much trouble but if you do its covered, you just pay the shipping charge and in the case of the EZAir units installed in the AC there is a slight charge for removal and reinstallation.
When buying the EZAir #5 for $860.00, its the most powerful unit of the plug ins,it makes since that you have powerful unit to kill mold and mildue etc., but also turn it down for small areas. The #5 would cover a house 2500 sqft. any smaller would only cover a room.
This investment can be sold and warranty is transferable. Stainless steel cases make it last for ever. You could get at lease high 3/4 or what you paid for it or maybe 1/2 . The longer you keep it the less it will cost you.