Our HPLC method test run is 13.2 minutes. You need ca. 35 minutes to start up the HPLC and condition the column at the beginning of the day and 40 minutes to clean the column at the end of the day. In between, you can inject continuously until you run out of samples. We have an autosampler with 45 samples capacity so HPLC would run those until all finished (or as programmed).
Assuming 4 samples per hour and 8-hour shift, you can do ca. 20-24 samples per day, depending on how you organize the receiving and extraction process. With the use of autosampler, you can leave the testing unattended.