I understand that most people are not perfect and will need to undergo some time in purgatory to get to heaven. I also understand that once someone is in heaven our prayers for him are no longer needed. How long should we pray for deceased friends and family members to make sure they make it out of purgatory?
Just keep praying for a person who has died whenever that person is brought to mind. I like to pray for the holy souls in purgatory during the consecration at Mass. Having a specific time at which to pray for that particular intention ensures that I don’t forget. I usually pray for all of the holy souls as a group and, specifically, for anyone who has died recently, for family and friends, and “for the soul most in need of Your [God’s] mercy.”