The presenter will be juggling his early morning Radio 2 breakfast show with on both programmes,
Evans, 49, will be saying goodbye to the Channel 4 show, which went off-air in 2000 but was recommissioned for a new series after a special aired in June.
“TFI Friday, this is the long goodbye now, because I’m not allowed to do any more TFI Fridays,” he said at the Radio Festival at the British Library in London.
Work on both programmes has begun with a series of TFI set for the run-up to Christmas and the first episode of Top Gear expected in May next year.
He added: “Time is in the mind. I do think you always find the time to do what you want to do, perhaps what you need to do. I am busier than I have ever been in one area of my life, but I’ve never had more spare time.”
“One of the problems with going crazy in this business is knowing there’s no light at the end of the tunnel, and because we’ve got a finite number of TFIs, we can meter that. We can pace that.”
He added: “Before, I did the whole Alice Cooper thing. I used to think you had to live the life to portray the life. Now I realise you don’t really have to do that, you can compartmentalise it. So that’s what I do now.”
Looking back at the TFI special, he said: “When we did the TFI special a couple of months ago, that was the happiest I have ever been on television. And I realised a lot through doing that special. That special did me as many favours as it did Channel 4 or anyone else.
“A lot of the time when I was doing TFI Friday, we were a little bit flying by the seat of our pants. It was great to watch but it was hell to make. The great thing about the special was, we were all old and we were all relaxed, and we knew we had a golden programme to present, so we could go and enjoy it.”
Evans, who took over the flagship motoring show from former hosts Jeremy Clarkson, James May and Richard Hammond, declined to answer a question about whether he could expect a congratulatory call from Clarkson if the series goes well when it returns in May.
He laughed off the question during an interview with radio presenter Paddy O’Connell, despite calling it a “brilliant question”, saying “that’s a far better question than any answer could be. Well let’s just leave it at the question”.
Reflecting on picking up the mantle from Clarkson, Hammond and May, he recalled his initial days after the appointment, when he asked how the former presenters had made the show: “I was asking them about the last incumbents and how they went about things. The answer was interesting to say the least.”
On his approach to presenting, he said: “I would love to be spikier, I would love to be a bit edgier sometimes but that’s not my job at the moment.
“Warmth is hugely important in mass entertainment. I am not flying a Spitfire, I am flying an Airbus 380 and we can’t do loop the loops. We have to get everyone across safely.”