Unless you’re alone on the course, most will consider it a huge breach of etiquette for unnecessarily holding up the groups behind you because you are hitting 2-3 balls per shot. Having said that, when out by myself, I will play 2 balls from time to time, but never at the expense of others’ pace of play. Generally, the expectation is for a group’s pace of play to fall somewhere between 4-4.5 hours.