There is a whole other aspect where airlines are not enforcing or charging extra for--YET. Size

from nwa, domestic Y gets two checked:

Luggage Measurement
Luggage is measured by adding length, width and height to determine the total number of linear inches/centimeters.
Northwest will accept luggage up to a maximum of 50 pounds (23 kg) and a total linear dimension of 62 inches (158 cm) at no charge.

Note 50 pounds, not 55 as other lines.

I have a large case that exactly hits the 62 inch limit. Mainly to go overseas almost empty and come back with purchases. I was shocked the first time I measured it and it hit the 62 inch limit, as I remember it being mid size in the store--there were lots there a whole lot bigger than the one I bought. I see lots at baggage claim that are bigger than mine. Some just huge.

At check in they weigh the bags, to give the pilot the cargo weight, and now to charge for overweight bags.

When they start measuring, lots of you will have to retire a lot of bags out there or get socked a fee every time. Your 26 x 18 x 10 is already 54 inches, only 8 short of max. And so easy to hit 50 pounds with.