This is from the UPS Support FAQs:
I tracked my shipment, and there haven't been scans on it in more than a day. What should I do?
Your package is moving within the UPS network and is going to be delivered on the scheduled delivery date. A package can remain in this status until delivery. Packages moving long distances are often not scanned again between origin and destination. Other than those receiving premium air service, packages may be delivered any time between the hours of 9:00 a.m. and 7:00 p.m. to residences, and close of business for commercial addresses. UPS cannot schedule a specific delivery time within that window.
I tracked my shipment, and there haven't been scans on it in more than a day. What should I do?
Your package is moving within the UPS network and is going to be delivered on the scheduled delivery date. A package can remain in this status until delivery. Packages moving long distances are often not scanned again between origin and destination. Other than those receiving premium air service, packages may be delivered any time between the hours of 9:00 a.m. and 7:00 p.m. to residences, and close of business for commercial addresses. UPS cannot schedule a specific delivery time within that window.