Hard to tell.
On one hand, long-lived puzzled are worth to be rewarded, and I quite like the idea.
On the other, honestly, I believe it won't be a stimul for solving the older puzzles - I bet no one here is against one or two more points to anyone.
At the same time it may lead to the appearance of so many unsolved puzzles that The Black Hole will be the biggest section of the forum... For instance, I can put a decent number of Soviet sportscars which I don't know myself as puzzles, and I'll be almost sure that it would be very hard for anyone to solve them.
Also, I think, it will be not too easy for administration to check for the 'year old' puzzles every day, or can this be done automatically?