in that song https://www.youtube.com/watch?v=7LzErRydJyE because I'm not sure about meaning
The it in "we can make it last" refers to the relationship between the singer and the object of their affection. The lyrics specifically say that they can make Dad's cash last but the true import is the preservation of that delightful if elusive moment when they decide to run away from the current trouble/boredom. The singer is hoping to preserve this in spite of the current difficulties and those that may follow. Such assurances are always worth the paper they are written on.