BUT! There is no real advantage to depositing with RCI more than a year before the check-in date unless you want to travel soon.
Actually, there is!
The maximum TPU value fluctuates with supply and demand, so you want to deposit when you think that max value is at its peak.
RCI has already demonstrated that they might (will?) increase the value of your deposit if that max value goes up, but have stated they will never decrease it once you have deposited. If the max value decreases over time, and you haven't deposited, you lose those potential extra points. If it increases over time, you still get them. I have one deposit that has seen (2) 1-point increases over the past year.
If you go into "My Account" and then click "View Trading Power Statement" in the lower right, you can see all of you deposits and credits, and where they came from. If you slick on "show detail" on any of them, you can see where RCI has made trading power adjustments.