Interesting to hear what everyone is saying about different sorts of
boots. I bought my Muck boots in 2009, and they only developed a crack on the top of the foot last year, but lasted pretty solidly for 9-10 years. I wear them every day for 3-6 months out of the year (I actually use them to cycle to work in the wet winters), with occasional use in the spring and summer. I keep them by the back door and slip them on when I need to do quick checks of things in the garden. It's squatting on my toes while weeding that's got them. That and the harsh, high-UV sun of the southern hemisphere. Maybe they don't make them like they used to? That's certainly true of just about every other consumer good.
As my boots are some of the most comfy I've ever had (and don't give me foot/knee/hip pain like regular gumboots), I plan to put a motorcycle tyre patch on the bend of the foot and replace the neoprene top at some stage. Hopefully that will revitalise them for pottering around in the garden and cycling to work again!