If you label your turtles, they store their programs. If your program includes a way to store the state it's in, then it can have a resume functionality. It's a pretty complex thing to code if you don't use GPS functionality to do so, but it does allow for the turtle to recover itself from a server crash and continue from where it left off. It's then, basically, always better than a quarry. Less resources to make, less resources to maintain, less resources to operate.
Many do consider cheating to mine without writing your own programs, some even consider cheating to use the default excavate command that comes with the turtle, which is basically, mine a X/Y area straight to bedrock. Do keep in mind the default excavate program is roughly 3 and something times slower than a BC3 quarry at full speed. It does come back up and store it's items in a chest if you place it behind it, and it does get fuel from a chest placed on the left of it's starting position now, so it's way better than when it was first implemented. Definitely something to consider if you dislike writing your own programs, but also dislike downloading programs other people made. This is built in with the turtle API, so there's that option. More advanced programs can be found in the computercraft forums if you have no qualms about downloading other people's programs that they made available to download. 99,9% of the time, running the excavate program will get you enough resources to get another turtle going on, then you can just keep adding to the turtle army.