We dont call to confirm, but dh takes all the confirmation numbers with him. I forget where but one restaurant lost our reservation. Since he had all the info, it wasnt a problem.
We never call to confirm and we have never had a problem. I take the confirmation numbers with me to each restaurant as well.
I believe each time you call, the CM opens your reservations file and also introduces the possibility of an error occuring. Once I have the confirmation numbers, I am good and I do not want to risk anything happening.
I just did because I couldn't navigate the site easily. Turns out I had double-booked a ressi for Il Mulino and Flying Fish and I thought I just had FF. I canceled the Il Mulino one.
I always call about a week before we go to confirm all the reservations and also take the confirmation numbers with us. I think I do it more for my own piece of mind we have never had any problems.