Unless you drive in very dusty conditions, a good cleaning of the oil bath filter will last a looong time. Years. Just clean the sump as it cruds up a half inch or so with sediment and dead wasps and leaves. They actually work better than paper filters. The big rigs still use them. Have one on two trucks and four tractors. Never dusted an engine in 50 years. Just keep the oil level up. Overfill and the carb will suck in the excess.