Water changes should be done whenever ammonia or nitrite read above zero. However, there can be a bit of leeway for ammonia, depending on the pH of the tank water. Water changes still need to be done but depending on the pH, it may be possible to allow ammonia to rise a little.
Ammonia exists in two forms in water, toxic ammonia and non-toxic ammonium, and the amount in each form varies with pH. At low pH there is virtually none on the toxic form while at high pH even a tiny amount of ammonia contains a fair amount of the toxic form. The first part of this link deals with the levels that are acceptable at varying pH during fish-in cycling
Part II SO YOU STILL WANT TO KEEP CYCLING WITH FISH? If you are determined to ignore the above advice in Part I and still think you want to proceed with a fish in cycle, then you need to be aware of the information presented below. SOME IMPORTANT FACTS ABOUT AMMONIA Ammonia in water exists...
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But there is no non-toxic form of nitrite. Once that shows up you will need to keep it at zero by water changes - or use the somewhat complicated calculation in the second part of that link for using salt to protect against nitrite.
You don't mention plants. Live plants take up ammonia as fertiliser, and they don't turn it into nitrite or nitrate. Fast growing and floatig plants are better at taking up ammonia than slow growing plants. If you don't already have live plants, even something like a few bunches of eldoea left to float will help to keep the fish safe.