This is a good question.
At CSSI, we have finished recoveries in 3 hours from book-in or if it was a firmware, or controller error, or a fried circuit board (usually lightning or power issues). However, if a drive has to go into the clean room, or require low-level mechanical work in one of our labs, it could take 5 to 10 days.
Every recovery is based on the merits of the condition of the drive, and our goal is to turn around the data as fast as possible. If it is a priority – our engineers can rotate and work 24 hours around the clock too.