Oh... I forgot to mention (post timed out) that it was through an article written by Jimmy Akin on plenary indulgences that I understood it was not necessary to confess every time if you are not attached to even the least venial sin. Something which he said is almost impossible to do. I wish I could remember where in my files I have that article.
There is a different answer to this question right here at Catholic Answers. Read the following:
To acquire a plenary indulgence, it is necessary to perform the work to which the indulgence is attached and to fulfill three conditions: sacramental confession, eucharistic Communion, and prayer for the intentions of the supreme pontiff. It is further required that all attachment to sin, even to venial sin, be absent. If this disposition is in any way less than complete, or if the prescribed three conditions are not fulfilled, the indulgence will be only partial. (ACI 7)
I leave it up to you to decide which answer is the correct one.
EDITED TO ADD...
I found the Jimmy Akin article... :extrahappy: scroll down the page to where it says "How to Get an Indulgence" and in the following lines he states:
The conditions may be performed "several days before or after the performance of the prescribed work" (norm 8). The document also established that a single confession may suffice for several plenary indulgences.
What Jimmy says agrees with what is in my "Manual of Indulgences" book in Norm 9 it says:
N9. A single sacramental confession suffices for gaining several plenary indulgences, but Communion must be received and prayers for the Supreme Pontiff's intentions recited for the gaining of each plenary indulgence.
So one confession can suffice for several days of "Plenary indulgences". Sorry that my answer was waaaaaaaaaaaaay too long LOL but I just wanted to be clear. My apologies.