I have some concerns about longevity of many of the current M1 machines. Yes, they have no moving parts other than keyboards (and fans in some models) which would be covered by AppleCare+ [1] so it would seem that you could keep on going a long time.
However, one of the non-moving parts does wear out: the SSD. It is not clear to me from the AppleCare+ TOS if an SSD failing due to reaching its write limits would be covered. The TOS says it does not cover wear and tear, but I'm not sure if SSD wear falls under that or not.
I like to keep computers a long time. I kept my 2008 Mac Pro until 2017, and only switched then because something I needed required the latest MacOS and 2017 was the year when the 2008 Mac Pro stopped getting the new major MacOS releases. I'm now only considering replacing the 2017 iMac i got then because the display has developed a vertical line of bad pixels. If not for that I'd be staying on it for another few years at least.
The SSD in my iMac is still around 98% after over 4 years and so seems like wear won't be a problem, and it is replaceable with some difficulty (OWC calls it an "advanced" repair and suggests having a pro do it).
But I've got 64 GB in the iMac. I don't think I've ever seen it touch the SSD for swap/paging [2]. I'm worried that on many of the M1 Macs that would not be the case. All of them except the Studio and the 14/16" MacBook Pros top out at 16 MB, and I've noticed on my iMac that I'm usually using between 16 GB and 28 GB.
I've watched quite a few reviews on YouTube of people testing the M1 machines under heavy load in quite a few different configurations, and one thing that has stood out is that there is surprising little performance difference in a lot of these tests between maxed out memory and minimal memory configurations. These tests do show significant swap usage on the low memory machines.
Similar thing in a lot of the comments on HN from developers using M1. Great performance with a lot less memory than I expect a machine used for heavy development to need.
I think what is going on is that there is so much bandwidth to internal SSDs now that on recent machines if you are hitting swap for task switching the I/O is so fast that it won't noticeably limit performance. It would only be when you are dealing with data structures big enough that you need to hit swap during random data structure access in a single task that you'd start really noticing a slowdown.
My concern then is that with the M1 Macs that have 16 GB or less RAM they may be making enough use of swap that they won't work out when it comes to longevity. Most people's needs grow over time as software becomes ever more bloated, so I'm worried that even if they aren't touching swap much now they will be in 3 or 4 years.
[1] In case anyone else missed this a year or so ago like I did, Apple changed the way AppleCare works. It used to be a one time purchase that extended your warranty to 3 years and then ended. They changed it so that you can buy it as an annual subscription that you can keep renewing indefinitely.
[2] Hah! In the middle of typing this post, my swap usage went to 99.0 MB. Kind of weird. I didn't manage to get any swap usage when I purposefully tried doing several large things trying to see how much memory I actually needed, and now I'm just sitting here with everything idle except the browser and I get swap.