Did you take into account the changes in orbital positions?
(giggle)
Nope, but as I understand it Saturn was at an optimal distance when the Saturn probe was sent. Saturn is 9+ AU from the sun. Uranus is 19+ AU. Since we're 1AU, then when we're at the maximum distance from either we add one AU to the distance, and when we're at the closest you subtract 1 AU form the distance, I don't see any changes in orbital positions significantly affecting what I said.