Gas water heaters, on average they last around 8 to 12 yrs and account for approximately 15 to 20% of your utility bill. So if your heater is showing signs it is looking at retirement, or if you're adding to or upgrading your bathroom.
Remember the three cardinal rules of shopping for a standard storage water heater: Take your time in choosing. Get a system that will do the job plus more. Find a heater that will do the job effectively but at the same time effectively doesn´t clear the wallet every bill.
There is nothing so motivating than having an icey-cold shower or a leaking gas water heater that is slowly flooding your basement, this all tends to make all the more urgent to get a new heater hooked up as quickly as possible. But if you choose one based solely on speed of delivery, you may end up with a unit that can´t keep up with household requirements, costs more to operate, and fails sooner than it should.