I'd still do routine maintenance but not really non-urgent repairs anymore. Worth of the vehicle is a factor as is how much longer it is likely to still be reliable.
For example: Jeep is at 240K-ish miles, 20 years old. Appraised tax value is $1200, market value is slightly less. It's leaking gear oil so am I going to take off the rear end, then find a machine shop to cut out the bearings, replace the seals, press in new bearings for $700? No, I'm just going to fill the differential with a quart of gear oil every two years. It's not environmentally responsible but repair cost is too great for a vehicle that's not likely to make it another 8 years - it also has a magical disappearing coolant act so it might be the 4.0 head issue.
I'll still buy the nicer-grade parts for things that affect safety, like Moog or Timken wheel hubs instead of Duralast or whatever. But the preventative maintenance stuff like belts, plugs, filters, leaky-but-accessible gaskets? Yeah I'll do them until the final death of the vehicle.