I have a third gen Prius with approximately 300,000 miles. I don't know because the mileage isn't shown anymore. Things currently broken include the multifunction display, the right rear window switch located on the driver's door card, the power steering rack is clunking and sloppy, the paint has peeled off, the subframe is bent so much that the plastic bumper cover doesn't even meet the subframe anymore, the front bumper cover looks like it's going to fall off soon in nine different locations and yet it still held on by zip ties, the suspension is starting to wear out again, the battery pack has already been replaced with an aftermarket pack brand new, break actuator/accumulator and abs assembly have been replaced, inverter converter assembly has been replaced, the 12 volt battery has been changed two times. The first engine already got a head gasket and then ultimately that went bad as well and I had to put any used engine 70,000 miles ago, the stereo display isn't readable anymore and some buttons don't work, the AC display is faded and unreadable, the steering wheel and driver seat look like crap, the entire interior looks like shit, somebody lost the shock absorber from the glove box door so it just pops open, the tray is missing from the armrest compartment, there are numerous dents and scratches all over the car, some of the third brake light bulbs are burnt out, the air conditioning tubing has been creased and probably restricts its flow somewhat, the brakes have been changed but that doesn't really matter in the big picture. Oh and the clock wire behind the steering wheel has been replaced before and none of the steering wheel buttons work anymore in spite of that fact because the steering wheel buttons are worn out, the stereo is worn out, the multifunction display doesn't show mileage anymore and some of its elements are burnt out. So what do you think should I keep fixing things and keep it running? Or should I toss it the next time something major goes bad?
Well, at 300,000, you've definitely gotten your money's worth, and then some, out of her! But, of course, the sentimental value, and memories, are still there. It sounds like a whole lot of her has, already, died....but it's your call!
It sounds like your skill level and tenacity has lumbered you with an indestructible beast. I do somewhat similar, albeit on a much more simplistic level: more than one of our knackered home appliances soldiers on without on/off switches. If I can find 'em I'll replace 'em, but if not, hey: it turns on when you plug it in.