The pump head is usually what fails because its lever clamp gets a workout. Mine finally failed. One side screws into the head, allowing access to the interior. That part started popping off.
I glued it down but then the lever that is screwed in started pulling out. Topeak sells a replacement head and hose, complete with parts for all their pumps, for about $20 online.
It was easy to replace. All I had to do was unthread the hose at the pump base using a wrench and then rethread the new hose by hand.
The pump head lasted at least 10 years. I don’t know when I bought the pump but I paid $30 and now it goes for $50. The only other maintenance you need to do is occasionally grease the plunger. It’s easy to access. Just pull back the tabbed plastic seal at the top and twist.
Jobst Brandt invented what he believed to be the best floor pump, a double-action behemoth. It was custom-built. I tried it once and found it hard to use. That was partly because the pump was built for his 6’5″ frame, but also because it was hard to pump. He claimed he could fill a standard road tire in 10 strokes.
While other double-action pumps have been made, the reviews have not been favorable.
My all-time favorite floor pump was Silca, but it had one irritating drawback. There isn’t a clamp at the pump head. You have to rely on the rubber washer inside the head to hold the presta valve. Those washers don’t last long before they lose their grip. They’re still sold online, but at more than $6 apiece, I’ll pass.