Had the HVAC tech out last week for the annual system check and he pointed out some rust bubbles forming on the bottom edge of the water heater. Being that's it's 9 years old, he suggested replacement sooner than later. Current unit is a Whirlpool 50 gallon electric with a bunch of electronic "power saver" wizardry at the control panel, and apparently supports a smart home connection.

Couple questions come to mind and was hoping to get some input from pros and folks who may have recently bought a WH:

1. House is 3 bdrm 2.5 bath, currently just 3 adults in the house, do I need 50 gal or will 40 gal do the job? Does smaller capacity save energy by having to keep less water hot in storage?
2. Is a glass-lined tank good? Seems like it would be but do they transport OK?
3. Do 12-year tanks really last 12 years, or should I get the cheaper 6-year tank and call it a day?
4. Any other important things to look for in a WH?

1. You do not get 50 gallons of hot water from a 50 gallon tank, so a 40 would be false economy.
2. YOu probably will not find anything other than glass lined tanks, economically.
3. The warranty has nothing to do with how long the tank lasts, only how long they will replace it. Many times a 9, 10, or 12 year tank is just a 6 year one with an extended warranty.