This is mostly just a good idea for fairly positive stuff. It is not wise to haphazardly ask for bad stuff. But pleasurable, positive, enjoyable memories, you can ask for those as long as you feel like.
For this purpose the client does not go back and relive incidents, she stays in the present and remembers them. Also we ignore any mechanisms of how different incidents might be associated with each other. We look directly at pictures or incidents, see what is there, and quickly go on to other pictures or incidents.
Remembering can be done along the lines of any collection of subjects, scales, aspects, or whatever. However, be aware that this is fairly light processing and we don't want to ask for traumatic incidents. Pleasurable experiences always work and otherwise anything that the client can face fairly comfortably.
Remembering can be done pretty much without limit. It can be done gradually until the point where one has full remembrance of a certain subject.
The only limiting factor is that remembrance by its very nature puts attention on the past. That isn't really were the action is. Life is happening in the present. Putting too much emphasis on the past might give the wrong impression that the past is important and that it somehow governs the present.
Remembering is done by gradually rehabilitating an abundance of experience and a tolerance of many different situations. It is a positive action. We are not looking for reasons, we are exercising flexibility.
Examples of directions for remembering:
"Remember a time when you succeeded"
"Remember a time you knew something"
"Remember a time you overcame a challenge"
or here is another way of doing it:
"Tell me a thing you like doing"
"Remember a time when you __"
"Remember another time when you __"
"Remember the earliest time you can when you __"