So I found a few old wallets from 2013. I can't wait for bitcoin-qt to rescan every time I replace the wallet.dat to check the balance.
are you using new install, latest bitcoin core version, to check them out?
do you mean redownloading the full blockchain? because rescan usually doesn't take much time
if you just need to dump private keys, turn off the sync or your internet connection
then just use
dumpwallet or
dumpprivkey commands on console
I'm using latest bitcoin core. And I can't use dumpprivkey on console because I don't know my wallet address!