My uncle is a high level engineer, and he knows that HDDs last several decades. The most consuming is the thermal part, that is when HDDs go up in heat, and down in heat - that's what eats them. The best way to preserve them is to keep them rolling, in a steady way. Like with combustion engines, to start one in freezing temperature, wears it down exponentially.
We do talk about mechanical factors, not electric.
I worked in a factory where they machined a lot of cast iron and was amazed how long computers lasted out in the shop. There was absolutely no routine maintenance on them. The windows 95 one we used to transfer programs from mainframe to CNC machine lasted until late 2006 before it died. I retired in 2010 and they still used a lot of Windows 2000 and NT boxes out in the shop. The CNC machine I ran flashed the oil temp and air temp constantly down at knee level oil cooler. In the summer temps in the 90's F were very common.
The term "routine maintenance" is interesting. We've been taught to defrag our disks, and several programs tell us to defrag even daily, and they suggest to do it automatically. Defragment is heavy for the disk, as it causes intense read / write. By doing that, it's like washing your clothes daily - they do wear, don't they?
I was talking about just cleaning the dirt out and checking fans etc. They must have a lot of iron dust inside out in the shops. I've wondered on the defragging obsession a lot of people have and it's affect.