My personal experience may be anecdotal but of the dozen or so folks, including myself, who took Paxlovid only one didn’t rebound.
I started symptoms on a Sunday night in May. Went to the hospital to get a real test, not a home test on Monday noon. Got positive results at noon on Tuesday and started Paxlovid that night as high fever was coming on. By Saturday morning I was 60% well and by Sunday noon 90% recovered.
73 and recent heavy chemo as I fought off stage 3 cancer in last three years. Your mileage may vary.