Is this direct RCI trades or something? I'm not really sure I understand how you would trade one week into 4?
I own one of the hotel chain weeks. Every year, I trade my unit in for points. And then a week through Interval costs $150 (exchange fee), plus some amount of points. A studio costs 23%* of my points (maximum) so I can get at least four of those a year. A one bedroom costs 46%* of my points, so I can get two a year. And a two bedroom costs 70%* of my points. In addition to that, I have the internal exchanges which can be leveraged for a considerable amount of time, doing four-day mid-week stays, and jumping down in season.
* These are high season numbers. If I stay in shoulder/low season, the point cost drops and I get even more time. The absolute maximum I could do, theoretically, is six weeks in low-season studios. And I don't even have a lot of points. Someone with a better week than mine could conceivably trade for 8 weeks.
