As I read more posts, I think I have a different way of looking at it.
UO Freeshards are a risky business. One day things are fine and the next, you've dropped fifty places on the top 100 and wonder what happened. A shard needs new players to join and for those players to stay. This creates more votes, retains a top spot, and the community will flourish. Here are the benefits I see to the age system.
New players feel they are given an incentive to start here instead of X shard. Age system starts you out stronger and more capable of getting into interesting content right away.
The rejuvenation potions, being obtainable, create another form of currency that could replace organics. The decaying bonus system ensures there will always be a market for rejuvenation potions. New players can farm them for gold/tokens/organics/pets/whatever knowing that there will always be a market for the items with players who have played a while.
The argument that I don't get is about avoiding the negative consequences. None of us will see a negative bonus until a real life year after the system goes in. Until then, you will be at least as strong as you are now statwise. This also creates a buffer to allow enough of the potions to get into the economy that nobody will have to suffer a doom and gloom situation.
So I see benefits to garnering new players, benefits to the economy, and very little detriment that may come to players in the summer of 2014 if they don't participate in any of the new item economy in the meantime (while benefiting from it for the next 12 months)