If you wish to speed up the digging even further, you can use a memory editor. Here are the relevant RAM values:

$036F: Countdown to next advancement. Decrements every moon phase change. Note that if you want an immediate advancement you need to set it to 01, not 00, as it is only checked *after* decrement and if it rolls over it just resets the countdown instead of advancing.

$0E0C-$0E15: Event flags for tunnel progress. If you just want to skip the wait entirely, set all of them to FF to instantly complete all the tunnels.

If you want to make your own hack that modifies the countdown values, they are stored at:
(values given in LoROM format)
$21BABF
$21BAC3
$21BAC7
$21BACB
$21BACF
$21BAD3
$21BAD7

There are multiple because a separate entry is read for every advancement. By default they are set to 10 (16 in decimal); this patch changes them to 08.