[kbutler]

The regret is because your purchasing decision would have been different if you had more information. In the case of "tomorrow it's free", the information is temporal (tomorrow's price) instead of spatial (the other store has a better price).

The amount of regret changes with the time span, largely because of the utility you gain in the interim, but the key is the incomplete information - if you had perfect knowledge, would you still make the same decision?

If you knew in 1998 that 10 years later, your computer would be virtually worthless, would you still have bought it? Sure. In fact, you did know the value would approach zero over time, so there's little need for regret beyond nostalgia.