Personally I think asking about warranty of such things is a waste of time. If you read the fine print it will always say that the base has to be prepared a certain way by a one-armed midget. That's their "out". And then the warranty is usually pro rated AND its only on replacement by their product which they're now selling you at full cost.

Just buy what you like and do a proper base for the product. If you're just going to slap new over old you're just asking for trouble.

I recently redid a bunch of floors in our 60-year old house. The kitchen had a full INCH of old underlay and flooring before I got down to the planking. Screwed all that down to get rid of the squeaks then 1/2" plywood screwed on top. Self leveler in a few spots to get it all dead nuts level then LVT (luxury vinyl tile) glued on top of that. So far so good !!