Hello, I would like to ask someone to help me figure out on what the life-span of the color filters depends. I have information that some of the monochromatic filters of an instrument will "break" after around 5 years when working with the instrument 3-4 hours a day. The filters are illuminated with 30-60 Watts thungsten-halogen bulb. I know that if the filter is illuminated long time (much more than 3-4 hours) with a strong light source some of the filters can melt. However, why would the filters "break" after using them regularly, but for 5 years? Are there any other causes that affect the life-span of the color filters? As a whole do the color filters have life-span? Thank you.