Swim work out length

Question
I am a 24yr old male at 5'8 with no prior profession training. I've always been interested in swimming. I finally have time to go to a lap pool and swim. I have finally taught my self, and with the help of others in the aquatic center, how to swim freestyle with correct technique and breathing. My question is: how long is a good normal swim work out? I've been swimming for about an hour a day. Should I swim more? I weigh 200lbs and I'm trying to get in better shape. Also, should I learn how to backstroke, breaststroke and butterfly? Will that give me a different workout?

I wish I would've started this sport at a much younger age. Any beginner tips will be helpful. Thank you  

Answer
Alan--
Sorry this took so long.  An hour or an hour and a half is a good place to start. And yes, you should work on learning the other strokes, it would give you some variety in your workouts and would help to tone a wider range of muscle groups.  During your workouts mix in some kicking drills and pulling only drills to change things up some.
The best beginner tips I can give you is to make sure your stroke and turn techniques are correct and smooth.  This will not only make your workouts more energy efficient it will also prevent injuries that can occur from doing the strokes wrong for a long period of time.

Congratulations on finally discovering swimming and good luck to you.
George