While I may not've cooked much, I'd say the time of marinating really depends on the meat, the marinade, and the intensity of flavor you want to settle with. One of the most common practices is you can have your meat pre-prepared by having it marinated overnight and get to cooking it by the next day.

I posted the question after I had marinated a pork loin for something like 18 hours. The flavor only got 30% from edge toward center. It was a little odd having the core of each slice without the same taste as the outer ring.