Speaking as a stockroom employee for a large science building a well-known university, it is unlikely to affect your delivery time. They have a set route to follow, and rarely vary from it - accordingly, the time of day is usually the same. Whether you have one package, a dozen, or forty (seriously), it doesn't make a difference. Your definition of "big" is subjective, but I would wager on an objective scale, given a computer build for a client with Newegg parts, not really that big - nothing that will really affect the UPS truck or driver.
The most likely reasons the delivery time could be different: holiday shipping policies may involve a second truck on the route, or the driver has been forced to vary their route for unrelated causes (emergency road closure, etc).