To keep from replacing the substrate, ever, a planted tank is a good idea. But it isn't as cheap to get started and you need lights for the plants.
I'm not sure how often you'd need to replace coconut coir, a few months?
A reptile carpet will need to be washed frequently, but not replaced frequently so there's that.
Paper towels are the option that needs to be replaced the most frequently.
Shallow water requires the same amount of maintenance as an aquarium, plus a filter, but as a bonus you don't have to change the water bowl every 1-2 days.

As you can see, everything has tradeoffs.