You are asking a question that cannot be answered with a give time.
Basically each store workflow (repairs) are different. Just think about taking your car to the dealership. It depends on who is staffed that day and if they have the parts to fix your car. Same with the Apple store.
Go to the Apple store, and stop trying to guess the turn around time. My concern would be more on the repair work not turn around time. I guess cause most user have a backup plan.. like using the other Macbook or iPhone or iPad

while they wait til the MBP is being repaired.