In your situation I would hang my hat on the manufacturers ‘determination’ of acceptable durability and quality of its products as being self serving. As a minimum I would challenge that in a way where the manufacturer had to put in writing their products are not very good, and go from there.
You might also troll through Choice reports on warranty experiences for the manufacturers as evidence. The manufacturer will be taking the position of the shortest possible life. Dispute strategy sometimes says to go for the most ambit claim and negotiate down from there, but the expected life for the product category is most reasonable when in dispute.
Rather than a pro rata refund, if you have not, go for a discount on a new one, from the retailer. Assuming 3/8 value was not delivered, using $1,200 as a possible purchase price, that would be a $450 discount, not so far off better sales campaign though.
A comparative personal experience w/Hoover and TGG is in this other topic.
