I have stamped H1B - Valid from sept 11 to Aug 14. But havent traveled till date. Is it compulsory to travel within a year or so or otherwise it will get lapsed or something
You may travel to US with this stamping until August 2014. If you want to travel after August 2014, you may go for stamping again, provided you have a valid I-797 at that time.
In any case, your I-797 should be valid when you travel and the petitioner (company) will support you in US.
Hope that helps.