It is not that a grhastha should live at home until he dies. Vanaprastha is preliminary to sannyasa. In the Krsna consciousness movement there are many young couples engaged in the Lord’s service. Eventually they are supposed to take vanaprastha, and after the vanaprastha stage the husband may take sannyasa in order to preach. The wife may then remain alone and serve the Deity or engage in other activities within the Krsna consciousness movement.
From Srila Prabhupada’s purport to Cc Madhya 24.260