After a month their rating drops. I had one pax whos rating was 4.9 after using uber for 3 years, but those are rare. Ive given 5 stars to PAX with 3.8 ratting and 1 star to pax with 4.8 rating.
I dont work the drunk shift; college kids. At times, i pick up pax around 1am who were out late for business meeting, some had few drinks, some are sober. Some get 2 stars and some get 5 stars. I play it by ear.