I wish there were publicly available data on this stuff, as we can only discuss anecdotes. In any case, in the neighborhoods I've lived in, it's not uncommon for UPS and Fedex to have zero deliveries at least one day of the week.

If Fedex is rolling around twice in one day, it's never the same line (that is, Fedex Express vs Ground/Home; Express incurs a special surcharge for residential deliveries and thus is usually only used by companies that primarily deliver to commercial addresses or who don't care about cost).

UPS is similar; usually, they only roll around in the evening, and when they roll around in the morning it's for one package with a specific delivery window obligation.

During December, of course, this goes by the wayside. Even USPS will roll around twice a day on the weekends leading up to Christmas.