Why would you just use a strut and keep the spring and mount that also have 250K on them? For $73 you get the whole thing and a quick install job. This is an old car with collision damage I am guessing he just wants to keep going for a while.
Same reason you recommend the $95 OEM motor mount when that $23 Anchor/DEA/eBay/whatever plain white box mount is so tempting. A while back I did some reading on those inexpensive struts on RockAuto for my budget-conscious neighbor. I don't remember specifics but I went away knowing I was not interested in them. Can't remember the name brand, Maybe OCS, maybe something else. If you've had good experiences with them, that's good to know and I put more faith in that than 20 anonymous guys on the internet.
Same reason I don't "tune up" a car by tossing and all the original Denso ignition coils in the trash and putting new ultra power coils on it because they are only $17 a piece.
My preference is to retain the factory springs. Rarely do I see cars with sagging springs. But what I do seem to notice is cars with funky stances due to what I assume are quick struts. While I do dig a 60s era, solid front axle gasser drag car with its nose to the sky, it's just not a good look for a 2003 Honda Accord.
An actual Shop with a proper wall mounted spring compressor can swap out a strut like a Nascar pit crew changes a tire. (Slight exaggeration). The strut assembly is coming off the car regardless.
Years back, I put some clearance Gabriel (I know they're no good) assemblies on a friends Sienna minivan. I was embarrassed by the +1.5" increase in ride height over factory. I think it may have eventually settled down a little bit. It was a beater and just got a tape measure alignment so no big deal.
This is all speculation when we don't know the actual condition or intended use of the original poster's Nissan. I have a car with 700k - runs and drives essentially like new. I don't automatically view 250k as nearing end-of-life. At around 400k I replaced the front strut/spring assemblies with some off a very low miles wreck (OEM). The originals I took off were totally fine, not leaking, so naturally I could tell no difference with the fresh ones. Still sports the factory rear shocks.
Just my anecdotal experiences, of course YMMV.
