Keep up the playing my friend. You will notice that very soon you will be developing righteous callouses on your fretting fingertips. Do not be alarmed. Wear these like badges of honor. :D


Just keep playing and eventually your body will adjust. I've played for 8+ hours before and not got tired. In fact, Steve Vai (you should look this guy up because he is awesome), has a 30 hour exercise routine (10 hours for 3 days). So there's virtually no limit to how long you can play with a little conditioning.


Some advice about starting lessons. I hope you luck out and get a teacher that makes you wanna keep playing. You will get frustrated, every neophyte guitarist does. In fact, I quit twice before my third attempt at learning guitar was successful in that I stuck with it. Have patience and believe that you will someday be able to play the songs your favorite guitarists play.


If you have any further questions I'd be more than happy to help you out. Good luck dude! :)