Yeah, four hours on the original leather seats in a 1969 MGB from London to Paignton. Didn't find them that bad. I don't find the original MX-5 seats any better.
Sorry to say it but they're a common swap because people are too cheap to go for the better seats that are available. In my opinion they suit the car and I don't think they are sympathetic for the era of car they are going in.
Personally I would opt for a paid of period bucket seats, like in the MGB LE50. But this is all my opinion, and it is your car, so feel free to tell me to STFU