When I replaced mine last year with factory rubber it only took a minute or two for each handle (front or back) once I figured out the first one. Yes, OE rubber cost a bit more, but it didn't give me any trouble.
I did do the drivers door on an E36 M3 coupe afterwards. And even though the procedure is the same it took 2 hours to do the one gasket and that was using factory rubber. The door card was off and it still took that long. Problem on those is the slider is behind a sheet of steel and rather a pain to get to.
Cosmos Black/Black 1995 540iA M-Sport
BMW Individual Exclusive Edition, 1 of 65 total, 9/25/95 Build