I've just reached that point. The catalyst for me was a significant devaluation in Turkish Miles value. (They more or less doubled the cost of redemption flights.) For some years I had been puting up with their lousy IT, redemption challenges and terrible customer service in return for their low threshold to reach Gold Status. But no more.

I'm retired so fly on my own money and usually fly business class (so I get most of the perks of Gold anyway). I have Priority Pass as a backup. The only thing I am giving up is shorter call centre queues (maybe) and lesser chance of upgrades (maybe).

My strategy now is to buy the "best" flight based upon a variety of factors rather than blindly choosing a Star Alliance option. I'll probably accrue miles to Delta for Skyteam because their miles don't expire, Qatar for OneWorld because their miles don't expire provided there is account activity (which is easy with Accor All membership) and Singapore for Star Alliance because they are my long-haul airline of choice and I can't find a Star Alliance program without expiry.

I'll stockpile my non-flying miles with Amex and a Mastercard that allow transfer to a wide range of airlines so I still expect to do a long-haul redemption every year or two for me and the mrs.

It takes quite a mental leap to make this decision after years of being blinkered to anything outside of *A but now it actually feels quite liberating.