Several points:
1. Someone suggested buying a "commercial" water heater.
Not sure that suggestion was serious or not, but for 20+ years, I used A. O. Smith BT251 commercial water heater in my apartment block. It only had a 60 US gallon tank, but it could keep up with the demand because it had a 251,000 BTU/hr input heat capacity. That is, when it fired up, the burner trays burned as much gas as you'd find in the furnace or boiler of a typical house. So, it was primarily the high recovery rate that prevented the water heater from running out of hot water, not it's storage capacity. Also, be aware that the massive heat exchangers in commercial gas fired water heaters make then very heavy. The BT251 water heater, for example, weighed every bit of 500 pounds and it took 3 people to move it down a flight of steps and 6 to move it up a flight of steps. And, I had to go through the hassle of replacing that water heater every 5 to 7 years because they never lasted longer than 7 years. In a residential setting, it might last longer, but you still have the heating up and cooling down of the heat exchanger that will limit the life of the unit. Commercial water heaters aren't made to store hot water like residential water heaters are. They're made to have super fast recovery rates so that they can keep up with 20+ tenants all wanting to shower and bathe first thing every weeekday morning, and so they're not really an economical option for a house where you don't need those high recovery rates.
If you want a POWERFUL water heater, consider buying a coil heater. A coil water heater has 4 components; the coil heater itself, a separate water storage tank, a pump and a thermostat. When the thermostat detects that the water in the tank has cooled down, it turns on the pump and the pump pumps that water through a copper coil that's heated by burning natural gas (or heating oil). The flame impinges directly on the copper tubing carrying the water, so the water heats up very quickly. The advantage of a coil heater is that you can use an insulated stainless steel storage tank so that you never have to replace the water storage tank. Also, the copper tubing coil in a coil heater can be replaced in an hour or two, and that's about the only thing that will ever go wrong with a coil heater. Coil heaters are very common in commercial settings like apartment blocks, hotels and car washes because by simply adding more storage tanks, you can have the same coil heater working all night to heat the water in a half dozen 200 gallon storage tanks to supply the demand for hot water first thing in the morning when 400 hotel guests all want to bathe and shower before heading off to the football game or convention. That is, they're well suited to situations where the demand for hot water can be minimal for hours on end, and then suddenly becomes very great for an hour or two each day.
An alternative would be to have two water heaters plumbed in parallel so that each unit heats half the water you use in your house. That way, if one water heater ever craps out on you, you can limp by on the remaining water heater until the first one is repaired or replaced. This is commonly done, but it's important that the resistance to flow through both water heaters be identical. There are ways to do that by making both the upstream and downstream piping to each water heater the same.
2. Someone suggested that you replace the (typically) plastic drain valve on your water heater with a ball valve and a drain valve. I can understand the concern about the cheap plastic drain valve on a water heater leaking, but if that ever happens, you can always stop the leak by just screwing a brass garden hose cap onto the hose thread of the plastic drain valve:
Just stick a hose washer in the cap and screw it onto the end of the heater's drain valve. Remove that hose cap whenever you want to open the plastic valve to flush out any sediment at the bottom of the heater.
And, you should drain the water out of the heater once a month until it runs clean, not just once a year.
3. Personally, I believe that the lifespan of a water heater is determined almost entirely by the proper sizing of the water heater based on the expected hot water useage of the household, and on the regular replacement of the anode rod in the tank to keep the steel tank galvanically protected. I believe that every company purchases and uses pretty much the same quality porcelain enamel lined tanks and anode rods. How long your water heater lasts depends on how much cumulative thermal shocking it has to endure. That is, how hot the metal of the tank gets when the heater is firing, and how cool it gets between firings. The higher the temperature peaks and the cooler the temperature valleys, the shorter the expected lifespan of the water heater. Proper sizing of the water heater will address this problem. The other is to replace the anode rod in the water heater every 5 years or so.