If the pork is fresh when you start and you don’t go past the grocer’s “use-by” date, you should have no problem. Marinating doesn’t alter the speed at which meat spoils. Of course, you have to keep it refrigerated and you don’t want it exposed the meat to lots of air. It should be tightly covered.
In the world of brining, people usually douse a whole pork roast for two to four days.
A nice way to marinate meat is to place it in a zipper-type storage bag with the marinade and squeeze out as much air as possible when you close the bag. Not only does this reduce the meat’s exposure to air, it keeps more of its surface in contact with the marinade while it lounges in your refrigerator.