Extending License Subscription

I have 141 days left on my NIS. I also have another license. How far ahead of the expiration date can I enter the new license and extend the subscription without losing time on the license? Thanks, Jerry

I have 141 days left on my NIS. I also have another license. How far ahead of the expiration date can I enter the new license and extend the subscription without losing time on the license? Thanks, Jerry

Many thanks. Jerry