In the beginning, people often choose puppets to be certain parts in a session, and then don't necessarily keep track of which puppets were which parts – in the next session, they may start over and use the puppets differently. As long as externalizing their parts using the puppets is helpful, I think it's fine to "start over," with the exception that any exile that is unburdened should be maintained – Dick says checking in with an unburdened exile every day for 30 days helps solidify the unburdening.
Puppets are an outstanding way to make sure you check back in with an unburdened exile for 30 days. You can place the puppet in a conspicuous place—like a bedside table or mantelpiece—to remind yourself to continue the relationship.
Or you can carry it around with you in your pocket or purse!
This picture is of my special silver bowl, which I use for parts I am giving extra attention. I keep it near my other puppets, but the bowl really singles out that particular part!