Ice Wine: vinos de hielo de Merlot

Also, what's the best way to store it?

The age-ability of the wine depends on how well it is made and how well balanced its elements are, just like with dry wines. For dessert wines, ACIDITY is the key, not alcohol or sugar.

In red wines, the tannins and acidity allow the wine to age for a long time, but only if they are in balance and there is ample fruit to last all that time.

In white wine, aging potential depends more on acidity rather than tannin. That is why the most age worthy white wines are those with ample acidity like German Rieslings, white Burgundy, and Sauternes.

A lot of the ice wines out there are lacking in acidity. It depends on what grape was used to make the ice wine. Ice wines are made from a number of different grapes (red and white) such as Vidal, Riesling, Gewurztraminer, Merlot and Cabernet Franc. I'd have more confidence in the ability of a Riesling ice wine to age well.

The sugar itself will not allow the wine to age for decades. They will keep for a few years, but are not expected to improve and will not go the distance for, say, a 25th anniversary.
A good, well balanced Sauternes, however, due to its higher acidity level, can last 20-30 years.
In summary, while ice wine is really good, the majority of them are not meant for long term aging. Enjoy them now.

Cheers!