When you mentioned your father repeatedly saying, "It's payback time," I felt like hearing my own father. I think it's a generational trait - during their time they think that it is the responsibility of the younger generation to tend to their needs just because they are the older generation. Then they cease going to work, not realizing that life does not stop when their eldest graduates from college and lands a job.
As breadwinners, we know the importance of helping out. But it is difficult to not pop the question, "Until when?"
I've even notice that even when you have your own family already, you still need to give back to your parents. It's really hard to set boundaries. Not all people are openminded. Some are still living in the old times.
I'm not sure if this is uniquely Filipino. There's no issue if we have the means, but if we are barely making it, the lack of support often leads to family rifts. Haay. Hehe. :)