Ward hitpoints and duration

I was just wondering, would it be such a bad thing to lower a ward's duration by how many hits it might've taken upon placement?

A ward typically lasts for three minutes, with three hitpoints, so were I to drop a ward in the middle of a baron/dragon fight and someone took a potshot at it before it went invisible, it should lower it's duration by how many hits it took, ie, two hitpoints left, two minutes left.

What would be the downsides?

/braces self