I have GE EV-1 controller from 1969. Works fine.the only certain way your Uncle will be able to drive his EV.
I don't think it even has electrolytic capacitors.
Semiconductors only being rated for 20 years.... come on man. 20 years ago was 1998. Yeah a few devices are going to go bad over time, but, it's not a plague (except for the capacitor plague, devices from early 2000s infamously fail due to attempted trade secret theft and counterfeit electrolyte failing).
It would certainly be easier to spend $100 on a little golf kart controller and be done with it, but, he's not condemned to failure just because he's using an old controller.