No. AM doesn't work in that way. Your miles expire in blocks. Your purchase of 2000 miles will expire in 3 years time and won't save those expire in 11/12.

There have been discussions here talking about how to extend your miles at minimal cost. (sorry can't find them out for you).

One way to do this is to use all your miles to get a long haul reward tickets, which covers up to 12 months, then cancel it at a cost at $120 USD. In that way the miles will be refunded to your account with a new expire date.