There is no need, according to 19 clause of MSLT. You can use an old one.
MICROSOFT SOFTWARE LICENSE TERMS
MICROSOFT OFFICE 2010 DESKTOP APPLICATION SOFTWARE
2. INSTALLATION AND USE RIGHTS.
a. One Copy per Device. You may install one copy of the software on one
device. That device is the “licensed device.”
b. Licensed Device. You may only use one copy of the software on the
licensed device at a time.
19. REASSIGN TO ANOTHER DEVICE. You may reassign the license to a
different device any number of times, but not more than one time every 90
days. If you reassign, that other device becomes the “licensed device.”
If you retire the licensed device due to hardware failure, you may
reassign the license sooner.