Preventive maintenance or just fix it when it breaks? What's worked for you?

I've been looking at some of the best used cars in UK lists recently as I'm thinking about changing my daily driver, and it got me wondering how other people approach maintenance once a car gets a bit older.

I've always tried to stay on top of servicing, change things before they're completely worn out, and sort advisories that come up on the MOT rather than waiting for them to become failures. A mate of mine does the exact opposite and only fixes things when they actually break, arguing there's no point spending money early.

With fuel prices, insurance and repair costs all seeming to creep up, I'm not sure which approach works out cheaper in the long run. I've had a couple of cars where preventive maintenance probably saved me from bigger bills, but I've also replaced parts that might have lasted another few years.

For those running older cars, do you stick to preventative maintenance or just deal with issues as they come up? Any examples where one approach definitely paid off (or backfired)? Interested to hear real-world experiences, especially from people dealing with MOTs, UK roads and higher-mileage cars.