For what it is worth, we have a Beneteau
OC50. So far (three years) no problems with the thruster. I cannot agree with the 'burning out' due to overuse theory. Any decent design of motor has thermal protection that is designed to prevent this. Also, when the bow thruster is used as part of a 'Dock & Go' system it can potentially get a lot more use than just a few seconds at a time (check out the official Beneteau
YouTube clips of this system being demonstrated - the only thing I feel for is the batteries).
I would pursue the warranty claim with vigour - don't take your dealers word for it - don't let them speak on behalf of Beneteau. In our experience Beneteau and our 'Dealer' are poles apart in their attitude toward after-sales service
. We would buy a Beneteau again in a flash.