[Cyberdemon]

You can purchase mileage up to 4 months till the end of your lease.

In your case that means you have up until your 24th month to decide how many more miles you need to purchase.

Absolutely no reason to purchase them now. If you don't use them, you don't get the money back. Plus if a year from now you move and start putting fewer miles on the car, it may balance back out.

Either way, better to wait until the last possible date, then calculate how far you've gone over and how much you project you'll be at the end of the lease and buy the miles then.