Activation may still be possible via the Telephone Activation Wizard if online servers are unresponsive.
While Microsoft won't actively break your installation (yet), they have stopped hosting easy downloads for many product keys. If your hard drive crashes tomorrow, that 25-character product key on the sticker or in your email is essentially a paperweight without the correct . office 2013 backup media
But without backup media, it is a ghost. Take 30 minutes today to hunt down that ISO and pair it with your key. Future "you" will be very grateful when you need to rebuild your PC after a crash. Activation may still be possible via the Telephone
If you are holding onto an Office 2013 license, do not assume Microsoft will host the files forever. Locate your product key, verify you have a copy of the installation media (ISO or IMG), and back it up to a USB or external hard drive today. But without backup media, it is a ghost