This is a tough call. We personally thought that the temples were so overrun with people (at least in mid Dec which is high season) that we could really only bear 2 or 3 days of it. Don't get me wrong, the temples and grounds are magical, one of the top 5 or 6 historical things I've seen in my life, but I really had a tough time with the crowds. It wasnt just crowds either, it was that one nationality (that will remain nameless) seems to come here in groups of 15-20 people with guides that either yell loud or carry portable amplifiers so that the whole crew of people in their group can hear them. That was one of the tackiest and most anoying things I have ever seen! For us, one of the most powerful moments was when our guide tried to read some of the old script that I had found on a wall, she explained it was different from modern script but she would do her best to read some of it for us. She's in the process of reading for us and the next thing we know there is a guy with a microphone next to us, shouting at his group, pushing his way in front of our guide. This kind of thing happened all day. Like I said, Ta Prom was better, especially at the time of day we visited. We decided if we went back to SE Asia we would go to the more remote sites, I hear that there are some places in/near Thailand border, etc. But if the crowds dont both you, I think you could spent a week here if you really wanted to see things and if you had a knowledgeable guide who could spend time and teach you about what you are seeing.