James May has said he and his co-presenters "became lazy" while making Top Gear, with just six or seven shows per series in contrast to the 12 episodes of his latest venture.
Television's motoring trio James, Jeremy Clarkson and Richard Hammond recently made their Amazon Prime debut with The Grand Tour.
The series received rave reviews from critics following its unveiling on the streaming service. The threesome then followed it up with the launch of a social content platform for motoring enthusiasts called Drivetribe.
"We'd become lazy with Top Gear, doing six or seven shows a series," he told the Christmas edition of Radio Times. "This is 12 shows. It takes a year to make. We had more energy in the old days, because we were younger and less knackered.
"I'm amazed this has lasted as long as it has."
The 53-year-old is currently promoting another series of his BBC Four show The Reassembler.
Last year, Jeremy left the corporation after his contract was not renewed due to a "fracas" with a show producer. His co-hosts Richard and James followed him in leaving Top Gear soon after.
"We have to accept that fairly soon, we will be too old for it," James said. "Richard Hammond (46) is a reasonably fit bloke who looks after himself. Me and Jeremy (56) aren't.
"Jeremy is particularly decrepit and I find growing within me - I try to fight it for some reason, but I'm giving in to it - a much stronger, nesty sort of instinct. Within the next five years, I don't want to be fart-arsing around."
Each episode of The Reassembler sees him taking apart objects before putting them back together.
Asked by the magazine if Jeremy would be a "welcome guest in his shed", James said: "No. He's not interested. We're so different. I don't want Jeremy Clarkson anywhere near my shed or my toolbox or my piano.
"He's interested in fashionable restaurants and celebrity gossip - I'm not interested in those."
The full interview is in this week's Christmas issue of Radio Times.