I did try disabling the separate graphics in the system settings (there’s a ton of troubleshooting I didn’t include because it’d bore you all) and this did improve performance, but the degeneration persisted. I even did some hardware fixes (I know a bit of electronics, enough to get myself in trouble) and that helped too, but all my fixes only prolonged the inevitable death of the machine. Eventually I gave the old 17" machine away, but I’d recommend posting the info in case others might be in similar straits and benefit from knowing the fix.
