That won’t take long. When we moved in to this house 40 years ago we had a water heater that we did not replace for 30 years and we have replaced it twice since. They aren’t making this stuff to last.
Be sure to have the anode rod replaced often.
That can more than double the life of the tank, and is very inexpensive. If you’re a DIY, it will be less than $20.
When the first one is pulled out you can see about how long it is until the next replacement is needed