Hi Grateful,
I would be very cautious and make some very careful value comparisons when you are looking at mattresses in this price range to make sure you are considering it for reasons that are important to you and that it really is a better choice in terms of PPP than mattresses that are in a much lower budget range.
You can read more about mattresses in more premium price ranges such as VI Springs in post #2 here and post #2 here.
I would also be aware that the warranty only covers defective workmanship or materials which is very different from the gradual loss of comfort and/or support over time which is the reason you would need to replace the mattress and a warranty has little to nothing to do with the useful life of a mattress (see post #174 here).
Once you are past about 10 years on a mattress then I would consider anything beyond that as a bonus and in some cases your own changing needs and preferences over time may lead to the need to replace a mattress even if it’s still in good condition.
When you are in these much higher budget ranges with more specialized mattresses I would also be very cautious about choosing a mattress that I hadn’t tested in person.
Phoenix