General Minimum volume suggestions amounts are listed below, it can last (depending on weather and temperature)
for about 6 to 8 months inside tire for temperate area, 4 to 6 months inside tire for tropical area
you can always add more than suggested volume to acquire a longer validity time inside the tire.
beyond validity time, just refill more, no need to clean.
General Volume Suggestion (for 1 tire)
For the customized tire, Please use below Calculating form to determine exactly how much volume to install