L1 extention while on i94

[pinkypv]

Hi - Am currently on L1B visa and my visa is expiring by March 2016, but i understand that i can extend my stay until my i 94 date which falls in Sept 2016.
Just wanted to know if i plan to apply for L1B extension, can the extension be filed in the month of July / August 2016.
What is the criteria for filling extension while staying in the US on a valid I94.

Any help is appreciated. Thanks!