A subs trial period how long should it be

I have a submissive friend that has a new potential dominate she told me she is on a trial before she becomes his sub .
she has to ware plugs from small to medium to large one size every day for a week the time she has to have it in is 1to 2 hrs each day for 7 days then move to next size for 7 more days then after the 3 weeks is up he moves to another stage .she has already Had 2 meetings so far with him and he does seem to be some what worthwhile he has also left her to have sub drop both meetings. I have had subs before and i never had a them do a trial for weeks nor have i ever left then alone to go thru subdrop alone.I guess im asking for Doms and subs how long have you had a trial go on and what did your Dom have you do and the Doms what was your time for a trial with a sub and your instructions before they became your sub?