Well... the duration of the high depends of a LOT of things... if you smoke very small amounts of weed, the high is short... if you smoke sativa ones (which give the mind high), the high is shorter than indica ones (which give the couchlock stone)...
I would risk that the "average" high peaks at 15-30 minutes, and lasts for some 2-3 hours. Note that after this 2-3 hours you will be almost completly sober, so in the time between the peak and the end of the high, it decreases, and you dont feel exactly high, but dont feel sober also. Its an intermediary state between this two ones.
But as you are just starting, if you smoke more im sure you will easily reach more than 1 hour being HIGH... and several (5 or +) until be sober again. Note, however, that if you smoke this much, the peak will be incredibly intense, even trippy. So, be prepared. :stoned:
Anyway... youre just starting... there is a lot of things about weed you will discover... just keep smoking! :thumbsup::jointsmile::rastasmoke: