"The WorldView-4 satellite has a design life of seven years; however it is expected to exceed this with ten to twelve years of service envisioned."
"The company’s first satellite, EarlyBird 1, was launched by a Start-1
rocket in December 1997. However, the spacecraft failed three days
A second satellite, Quickbird-1, was lost in a Kosmos-3M launch
failure in November 2000, before Quickbird-2 successfully reached orbit
atop a Delta II the following October, achieving thirteen and a quarter
years of service before its retirement in January 2015."
So somewhere between zero, three days, and 13.75 years...averages to 4.5 years