Its definitely possible. The easiest way to experience this straight up though, is to dilate time, or as Sageous has mentioned before, you could even destroy the entire concept of time in dreams completely. This would allow you to stay in the dream world for as long as you wanted, but I have yet to find out just how to do this. I'd start out with dilating time, which has endless possibilities to how long you could stay in. 70 years may sound far fetched, but I think its completely possible. In dreams, whatever you can imagine, you can do. You just have to have the control to be able to manifest those things.