The germicidal UVC tubes 3ELEK0001 is changed once a year (9000 hours).
Of course, this is a manufacturer’s recommendation.

For a precise explanation :
We know that 365 days = 8760 hours.
If we use the product 8 to 10 hours a day and exclude holidays/weekends, we will be at 250 days of use which means 2000 to 2500 hours of use.

We have to consider that the use is 3 to 4 times longer than the recommendation (Filter = 1 times/year & Tubes = 1 times/3 years).