Yes. Often you'll do 3 - 5 tastings a week, sometimes even two in a day so spitting really helps keep the alcohol intake down.
The thing that really gets you is palette exhaustion though. Taste 40 ripe Cali cabs and they all start tasting the same after a point...
(If someone wants to search for the term, also try "palate fatigue")
Meanwhile...there is an argument somewhere about the stomach being the 2nd brain. I don't know how you can reasonably taste without swallowing wine (while understanding it's a far more reasonable way to go for the pros).