That's too much time there IMO, if you have a choice. Furthermore, I know if my daycare pushed to keep my child for an extra day, I'd start looking for a different place. I'd start wondering if it were a kiddie-mill as they're sometimes called, when the center's goal is to pack as many children in there as legally possible so they can make a profit. No daycare worth it's salt would push to "unnecessarily" monopolize a child's schedule. It is daycare, not an academic program that will benefit their entrance into a college.
I think young kids need to be with their mommies. Daycare is only necessary for those who must work, but they're NOT necessary for a child to properly develop emotionally, socially, or academically as they're NOT actual school but can be a preparation for school.
We sometimes forget a parent is a child's primary teacher and a parent is truly the only one who can best love and nurture their own children. For those who don't have a choice, sending our children to a daycare that offers more than a place to stay such as a montessori program, or is an opportunity for our children to play with others can be comforting. However, the truth is, when they (children) are small, it is always best if they can be home with their parents. The more time a parent can spend with their child, the better. Not to mention no one wants to miss those once in a lifetime milestones and memories. If you are blessed enough to have a choice in the matter, and more daycare hours are not a necessity, then go with your gut and spend that time with your child. Volunteering can wait for when your child is in high school and no longer wants to be home with you because they're itching to spread their wings and start their own lives. It comes quicker than you know.