If you plan on making a long-term backup, for the purpose of safeguard against data loss, after encrypting with a passphrase, you might consider starting Bitcoin once with a large keypool option such as bitcoin-qt -keypool=2000. This will fill the wallet with future keys that will keep your backup from becoming obsolete for a long time.
Good idea. Do I change it in the shortcut properties, or somewhere within the program itself?
Another question: If I kept my wallet in cold storage, and I deposit more coins to a known address in that cold storage wallet, does that change the number of keys in use? How would that affect the existing unused keypool?