5 years in L1 and 3 years in H1 continuously possible?

Hi There,

I am working on L1 since January 2008 in USA. I have filed H1 this year and got it approved for 3 years which is till Sep 2015. This is beyond the H1 cap of 6 years, Can I still stay in US continuously till 2015 as the I 797-A is valid till Sep 2015 or I will have to go back voluntarily in 2014 after completion of 6 years

This may be a mistake on part of USCIS. I would suggest leaving US after you complete 6 years inside US even if your petition is still valid.