It is easy to overgeneralize, and oversimplify the replies to a topic.
I see posts about spending a boatload on a nice spring compressor, and posts about using cheaper parts as if any vehicle a few years older is already trash and not worth bothering.
Any vehicle you want to continue using with more than bare minimum value (say $1500 or less) should get parts deemed mid-grade at a minimum unless the vehicle has some other outstanding issue that you expect will end its life soon... not just "it's old" or "I don't like that make/model/whatever".
If the original springs are sagging, absolutely replacement springs are worthwhile unless the budget is so extremely tight that you can't justify it but then, don't even replace struts unless an inspection mandated it. Otherwise, if the OEM springs aren't sagging or are sagging equally between front and rear and you are only trying to meet a safety inspection mandate, replacing only one axle with quick struts can make the ride height and handling uneven, or even worse if you are only replacing the single strut that failed the inspection.
I don't usually wait till a vehicle is low value to replace the struts. In my area there are many hills and curves and a passenger sedan might make it close to 100K mi but anything, even a minivan potentially hauling a load, I'd replace struts on closer to 50K mi and at that point the vehicle has a lot of value left in it even if seldom driven so the bluebook value is less than the true value to the owner. This is very often the case for people who maintain their vehicles well.
In other words you can let a vehicle degrade not just from failure to maintain it but also by using inferior parts to the point where you compromise the ride, and expectation of time till same repairs need done again, even on a wear item like struts there is the frequency in which you have to redo the repair with new ones.
Getting the new parts along with the struts is good for cheap repairs on vehicles long past due but I've never needed more than the strut itself for the first strut replacement. I usually try to time it along with 3rd (2nd after the factory set of) tires so an alignment is done just before new tires, which puts it somewhere south of 100K mi., closer to 50K mi.
Anyway back to my opening statement, each vehicle design, environment and driver is different. It's not cut and dry how much to replace except after considering all the variables including budget, but generalizing (lol) if the budget is tight or the vehicle has limited time left on the road, I'd only replace the strut itself. More often than not I wouldn't use quick struts and especially not the lowest cost you can find, unless you come across some beater and are just trying to flip it and let everyone else deal with it later so you can increase profit yourself.
Some might say that adds value to the vehicle and it might, depends on what the buyer wanted, just road worthy for a while at lowest cost or if they instead didn't want the sale value increased when they'd rather do it better themselves.
Ultimately my biggest issue is when someone tries to act like low value vehicle deserves garbage parts, when if it was just maintained properly it wouldn't be slipping into the grave in the first place. It is madness that people today act like a 15+ year old vehicle should be scrapped for the metal value, when bluebook only assumes that is what the owner let happen instead of good maintenance with good parts.
The sad truth is that my oldest vehicles are my best ones, in that they will cost me less in the long run to keep on the road than the newer ones. Granted I drive the newer more often but already got those miles out of the older ones so still a reasonable comparison.
often just getting down the road another year or so for the minimum amount of cash is exactly the right call
I'd not bother at all for a vehicle you think has only a year left. Seriously? If you're going to let a vehicle decay to that point, sell or scap it already, not pouring money into junk parts. If it only has a year left it is worth sub-$1000 so quick struts and the needed alignment are not at all a good investment, at that point it's a mechanics special and just has to drive away from its location to the new owner's location.