L1B to L1A

[achowdhury]

HI all, I am a new member here. I have a L1 B blanket visa and want to apply for GC. I heard that applying for GC with L1A take much less time compared to L1B (as labour part can be skipped). So my question is, can I apply for L1B to L1A transfer now (my L1 B is valid for 3 more years) or it can only be done before L1B expires. BTW, I am in a managerial role in onsite.

Thanks in advance.