For most practitioners the treatment is more commonly priced per treatment not for the length of time you are on the table being treated.
EXAMPLE – When you take your automobile in for repair they charge the full hourly shop rate with a minimum charge of one hour in nearly every case. Even though you may just need an alternator replaced, it may take the mechanic only 15 minutes to remove two bolts while
unloosening the belt, unclip one set of wires, remove the alternator, put in the new alternator, re-clip the wires, and tighten the two bolts and a belt. The charge will still be the minimum one-hour shop rate and your vehicle is as good as new again.  The bottom line is what needed fixing was fixed and you are off again.