The right answer is: It depends.
1. Check the pressure on the pressure gauge. If it's too high it's time to clean it
2. Take into consideration the size of your swimming pool and the size of your pool filter. If your pool was fitted with a smaller than recommended pool filter, you are gonna have to clean it more often.
3. If your swimming pool has vegetation around it that sheds a lot of small debris like little seeds or leaves, then its a good idea to clean it more frequently as these get stuck in between the pool filter cartridge's pleats.
4. If you clean the cartridge too often like every week, it will last you less and also you are not allowing it to work at its best: the dirtier the cartridge is, the more small particles it collects.
Related: How To Clean The Pool Filter