How Often Should T8 Tubes Be Replaced

[Egmel]

As it's often difficult to tell on a day to day basis whether lamps are dimming does anyone have any recommendations how often lamps should be replaced?

 

[SuperColey1]

once a year is what most people say. I think thats about right. a little longer if using an electronic ballast as it doesn't flicker start like magnetic ones and the flickering start wears the bulb out quicker.

Andy