Are you putting the fish directly into your DT without quarantine? If so, then you do need to drip acclimate, but only if your salinity and the fish bag water salinity are different. If they are the same salinity, or really close, then no drip required...just float the bag to equalize the temperatures. But if you are drip acclimating to go into your DT, then 15-30 min is probably sufficient. Check the water to see that the salinity is the same as your tank...then you are ready!
If putting the fish into a quarantine tank, then you have a better option...match the salinity of the QT to the salinity of the fish bag water! Then you don't have to acclimate...you just need to float the bag for about 15-20min to get the temperatures the same...then release the fish into the quarantine tank! Then, slowly raise the quarantine tank salinity up to your DT salinity over the next week or so during observation.