How much oil is used per tank?

[Cam]

1987 V20 fish (cuddy) with 1996 V6 Johnson Oceanpro 150. Just replaced VRO pump on this new to me boat and was just wondering what kind of distance/hours does 2 stroke oil generally last? First time out in boat with family, I burned 45 gallons of fuel (took a trip around Staten Island and visited Statue of Liberty). I put the boat, I feel, through it's paces. and after I fueled up, I forgot to check the VRO tank. I know I physically put in 1 gallon before trip at first fillup. Just wondering if I should refill before using again. Thanks. (no pics yet)