I do not do them unless bonused as there is no visit fee or wait time max. They used to state that if you were not helped in 30 minutes, to leave and come back later. I try to arrange other nearby shops. If busy, I'll ask if it will be awhile before they can see me. I may leave and come back.
Generally I get them done that day. There is a time frame, but I generally do not like to return. The reports are very easy. Interestingly, they have shoppers picking them up at the regular price the last two months so I have only done one. A relief as I have shopped so many of the branches 3-4 times a year that I kept a book on who I talked to. There are 4 that I will not shop as the manager has been there for many years and most likely I would get them again.
Do not read so much, look about you and think of what you see there.
Richard Feynman-- letter to Ashok Arora, 4 January 1967, published in Perfectly Reasonable Deviations from the Beaten Track (2005) p. 230