After a while, once the valuable card has reached its top value, people forget about the mid cards and the deck/set can be resold for 10 to 40% more of it’s $ value, making 1$ worth up to 1.4Tix!

Time limited set/deck with new cards, like the commanders, also appear to be good in the long run.

Is there any time limit for special set still available on Mtgo? like the planechase 2012?

No, we don’t have a good idea about the popularity of FTV sets. But, roughly I would say that if there is ‘value’ in FTV:20, it will be bought, opened and resold until the ‘value’ disappears. There will also be people willing to buy and hold these for the future.

My general take on special sets is to not speculate on them, but consider closely how they could affect original printings. Typically they put a price cap on the original printing.

The best example I remember is when Stoneforge Mystic was in a precon. The WWK version got up to 15 tix at one point, which was the highest price a mythic era rare had reached to date. That didn’t last though, because the precon had 3 copies in it, and you could buy that for less than what 3 WWK SFMs sold for.

Mutavault has been confirmed to be in M14, and rumors are that Thoughtseize is included in the core set as well. That will be interesting!