There is no fixed standard and it is influenced by various factors, as follows:
Usage temperature: In a temperature environment of 200 ℃ -300 ℃, if there are no other complex corrosion factors, high-quality organic silicon high-temperature resistant coatings can generally be used for 5-10 years or even longer. Long term use in high temperature environments ranging from 400 ℃ to 600 ℃ may result in performance degradation and coating aging of typical organic silicon high-temperature resistant coatings within 2-5 years. Some special formula coatings can withstand high temperatures of 1300 ℃ for a short period of time, but their service life may only be a few months or even shorter when repeatedly used at this extreme high temperature.
Environmental factors: In outdoor atmospheric environments, under harsh conditions such as strong ultraviolet radiation, acid rain, and high humidity, the service life of organic silicon high-temperature resistant coatings may be shortened to 3-5 years. If it is in an industrial environment with chemical corrosive media, such as strong acids, alkalis, organic solvents, etc. in the petrochemical industry, the service life of the coating will be significantly shortened, and maintenance or replacement may be required within 1-3 years.
Coating thickness: When the coating thickness is uniform and meets the specified requirements, generally speaking, organic silicon high-temperature resistant coatings with a dry film thickness of about 100-200 microns will have relatively good protective performance and service life, and can be used for 5-8 years in normal environments. If the coating is too thin, such as less than 50 microns, there may be a decrease in protective performance within 2-3 years.
Construction quality: Before construction, the surface treatment of the substrate should meet good standards such as Sa2.5, and the construction process should be strictly carried out in accordance with the process requirements, such as using appropriate construction methods and constructing under suitable temperature and humidity conditions. In this way, the service life of the organic silicon high-temperature resistant coating can meet the design expectations, usually 5-10 years. If the construction is not standardized, such as incomplete surface treatment, bubbles, sagging, and uneven thickness in the coating, it may cause the coating to fail within 1-2 years.
Substrate type: On metal substrates such as steel, if the metal itself is prone to rusting and the environment is harsh, even with the protection of organic silicon high-temperature resistant coatings, the service life may only be 3-5 years. For inorganic non-metallic substrates such as ceramics and glass, the adhesion with organic silicon high-temperature resistant coatings is relatively good. If the usage environment is not particularly harsh, the service life of the coating may reach 5-10 years.

Room termperature curing polysilazane, pls check IOTA 9150, IOTA 9150K.    
High termperature curing polysilazane, pls check IOTA 9108, IOTA 9118.