Is this a normal part of friendship?

I have this great friend and we spend a lot of time together. Because we usually have so much fun, we wind up spending hours on end with each other, like from early afternoon til late at night. The thing is we are very different and our personalities kind of conflict. As the night wares on it seems like we begin to grow a little tired of each other and things that the other did earlier which seemed funny now just seem annoying or frustrating. My friend who is usually very hyperactive seems to really mellow out and become almost sullen. This is around the time we usually part ways. The next time we see each other, maybe a day or two later, everything is perfectly fine as if there had never been any tension. Is this normal? Do people just grow tired of each other after a while? It also may be the fact that we usually hang out til 1 or 2 in the morning so we'd naturally be pretty tired.