My buddy Tyler and I went throwing outside and I set up the video camera to capture our throws. Getting out and throwing with someone is a great way to work on your throws but make sure to focus on having good form and thinking about where you want your throws to go. Also, learn how the disc moves through the air and practice reading the disc so you’ll be a better receiver/defender in a game.
Usually when I go throwing (I usually throw with my girlfriend actually), I train 1 or 2 throws per session. For example, I will train my forehand huck. A session should never last for longer than about 1 hour, because you'll lose form due to tiredness and then the training will miss its effect.
I disagree with the 1 hour but I do agree that once you start losing form and you're not really learning you should stop.
Case in point…I usually go for 2 hours when I throw. I'll start with a warmup, different lengths of throws, different throws, different drills, etc. I treat it very much like a driving range for golf.