We have quite a few pilots on 75 and 50% contracts. The common comment for all I have spoken to is 'wish I had done it years ago'.
The other common thread in these conversations is that mostly they are in their late 50's or early 60's. Twenty years ago all these people would have been retired, but for various reasons have to or want to carry on and the mind maybe willing, but the flesh struggles to cope. It's well documented that shift work and night work reduce your life span.