Retirement
24 “This is the rule the Levites must follow: They must begin serving in the Tabernacle at the age of twenty-five, 25 and they must retire at the age of fifty. 26 After retirement they may assist their fellow Levites by serving as guards at the Tabernacle, but they may not officiate in the service. This is how you must assign duties to the Levites.”
Numbers 8:24-26 NLT
This is the only time retirement is mentioned in the bible; and seems to be specific ONLY to the Levites.
The History of Retirement Wikipedia page suggests that retirement is a relatively new phenomenon that began gaining steam in the 1800's. Furthermore the Wikipedia page states that "according to the Mental Health Foundation, one in five of present-day retirees experiences depression." Who wants that? But to be fair how many non retirees experience depression?
Bottomline: Should Christians be fixated on retirement like many others in this world? No, not if you're healthy and able to work.