TireJect is designed to prevent flat tires for up to 12 months in most applications. The storage conditions, climate and frequency of use all factor in to how long TireJect will continue preventing flat tires - refer to "How long does TireJect Tire Sealant last?" for more information on your vehicle type.
If it has been several months since your last application typically re-adding half the initial dosage amount will solve the issue. For lower speed applications like lawn mowers and tractors you might want to consider increasing the dosage amount to extend the life of the tire sealant. Over time the tire sealant is building a thin rubber film around the inside of the tire and increasing the dosage amount will allow you to go longer between re-applications. We only recommend doing this for lower speed applications because you might get tire vibration if adding to much tire sealant for vehicles that travel over 10mph.
TireJect will seal any leaks in a tire caused by bead leaks, tread and sidewall punctures up to 3/8" and even mild tire dry rot. If fresh tire sealant is installed and the tire is still going flat you might want to check if the leak is coming from the valve stem.