Also, whenever something did go seriously wonky following an upgrade, it was usually fixed within a few days.
That doesn't sound too bad -- though ATM I'm hoping to use it as a host OS from which to run guest OSes via VirtualBox, so if VirtualBox stops working, that doesn't sound so good.
I guess the best way to think about it is to remember you're running Debian rather than Ubuntu with LMDE - with all that implies. If you let that understanding guide your decision and expectations there shouldn't be any bad surprises. If you've had previous experience with Debian you should be fine. If not, you'll possibly need to learn a little more. But learning something new is always a good thing, so no knock there.
Actually although not so much recently, Debian is what I've had the most experience with so that should be ok. I'd still be using them mostly if I had figured out a satisfactory way to run newer software (for that Arch seems to have worked out -- and Gentoo was ok for that too). Though performance might suffer a little, am currently leaning toward experimental / new things running in a guest OS.
I looked around a bit for a distribution that tries to provide a minimal environment with VirtualBox but though I've seen queries that seem to ask for that sort of thing I haven't found one that looks good yet.
Addenda: regarding approach...
I have the luxury of having several machines at my disposal. So what I do (and would do even if I only had one machine) is throw a new drive into whatever I'm installing on and go from there. I'll keep a new distro up for a week or two, to see how well it works for me, and decide if I like it. (Just because it works doesn't mean I'll want to spend my workday using it. These days I expect more than "just works" from a distro.)
If it makes it past a few weeks with no major disasters or showstoppers - and find myself using the new distro more and more - it's a keeper. If I really
love it, I'll install it on everything. If I just like
it, I'll keep it on whatever it's running on and leave the other machines as is. (FWIW I'll usually have two or three distros running on my network at any point in time.) Over time. and with day to day use. there's usually one distro I find myself obviously gravitating towards. That becomes my go-to distro until something I "really
like" more comes along. It's kind of an organic approach to distro selection and deployment. But it works for me. YMMV.
Sounds like a decent approach -- I think I'd try that if I had a spare machine. Perhaps I can just run something as a guest OS for a bit as a partial test in the mean time.
Regarding LMDE though, I guess it's not likely one can transition (settings and all) easily from Petra -- reinstall from scratch is probably a better approach, huh?