Ash and oak last for decades if they get a little attention. Here is the routine we use on our own boards.
After every use
Rinse with warm water, wipe with a damp cloth and let the board dry standing on its edge. Never leave it in the sink and never put it in the dishwasher.
Once a month
Rub a spoonful of food-safe oil into both sides, leave it overnight and wipe off what the wood has not taken. Linseed or a mineral oil both work; olive oil can turn rancid.
When it looks tired
Light scratches disappear with fine sandpaper, grit 240, along the grain. Oil it afterwards and the board looks new again.