TN/TD renewal by mail service

How many months it will take if I mail application with copies to USCIS? I live in Texas and can not go to border every year.

If I do not have any replies from USCIS for several months where to contact officers. Thank you for the help.

Not long these days for USCIS TN processing, but as long as you timely file the petition, you can work for the petitioner for up to 240 days with the pending approval.