Depends on the tip and the type of top. Bearing tops don’t need pointy points since the tip is supposed to stay still, so a plastic bearing king tip can last quite a while. A Rip Cord tip will get pretty dull if you drop it on a hard or rough surface, and you can either try and sand the burrs off or get a new tip. You don’t really want it sharp, just not jagged. Steel tips are therefore much better for fixed tip tops, but still a nice feature for bearing tops. You really shouldn’t have to replace a steel tip for quite some time unless you like to spin it on concrete every day or something.