When Peter Frampton put out a press release Thursday announcing his “farewell tour,” there was cause for cynicism, given the rash of rockers putting that tag on their outings to goose ticket sales for what may or may not turn out to be their last go-round. But although the initial alert didn’t mention it, the singer-guitarist had a better reason than most for warning fans that this is probably it. Frampton wants to get his last licks in ahead of the progression of a rare degenerative disease he says is bound to affect his playing.

He told “CBS This Morning: Saturday” that he suffers from a rare and incurable condition called inclusion body myositis, which causes muscles to slowly weaken over time. Although the disease was first diagnosed three and a half years ago after he had a tumble on stage, it was only this past fall that he noticed the effects speeding up, so he decided it was time to tell fans that this was their last shot at seeing him in peak form.

“The reason I’m calling it the ‘farewell tour,’ again, is because I know that I will be at the top of my game for this tour and I will make it through this and people won’t be saying, ‘Oh you know, he can’t play as good.’ I can. But we just don’t know for how long,” he told co-host Anthony Mason. While he’s confident he can deliver this summer and fall, “in a year’s time, maybe not so good. I’m a perfectionist and I do not want to go out there and feel like, ‘Oh I can’t, this isn’t good.’ That would be a nightmare for me,” he said. “I’ve been playing guitar for 60 years. Started when I was 8 and now I’m 68. So I’ve had a very good run.”

Frampton acknowledged that his children had a rough time with it when he first informed them of the diagnosis, “but I said, ‘Look, it’s not life-threatening. It’s life-changing.’ … They’ve been phenomenal, everyone. Every one of my ex-wives have been wonderful, I have to say,” he added with a laugh.

The tour begins June 18 in Tulsa and is scheduled to wrap up Oct. 12 in San Francisco. Although most of the dates are in theaters and amphitheaters, he will be hitting two arenas that are as iconic as “Frampton Comes Alive”: Madison Square Garden on Sept. 13 and the Los Angeles-area Forum Oct. 5. (Jason Bonham’s Led Zeppelin tribute band will open the shows.)

Frampton told CBS that it has affected his legs more than his fingers, for the most part — hence the falls that led him to seek a diagnosis. “Going upstairs and downstairs is the hardest thing for me,” he said. “I’m going to have to get a cane … and then the other thing I noticed, I can’t put things up over my head.”

Frampton told Rolling Stone that he expects the condition to affect his playing ability but not his singing voice. “There is another part to the disease that can affect swallowing, but it’s only 50 percent of the people that have it. I don’t have it, thank goodness,” he said. As for the rarity of the condition, “It’s a very boutique — I hate to use that word, but it is — disease. Only 24,000 people in this country know they have it. But I’m sure there’s a lot more that just think they are getting old like I did.”

He’s not ruling out a European extension next year, his condition permitting. “We might be able to do the same thing on a limited basis in Europe in the spring of the following year, but I don’t know that yet,” he told the magazine. “I’m going to be playing as long as I can play, but this will be the last extended tour. I can’t say what I’ll be doing next year.”

He struck a resilient chord with CBS. “I’m thinking of all the times in my life that I have something devastating has happened to my career or in my family or me. I’ve brushed myself off, got myself up and changed directions,” he said.

And so he’s not ruling out an after-the-farewell tour, although he notes that the thin prospects for a cure make that far unlikelier than it would be for some other rock acts who’ve found it in themselves to keep going after saying goodbye.

“Maybe if the drug trial works, there’ll be the miracle tour,” said Frampton, who is being treated experimentally at Johns Hopkins. “I wish, but I’m realistic, too, so that’s why … this really is the farewell tour.”