Replacing T5 Bulbs

[MorganAtlanta]

I know the recommendation on here is to replace florescent bulbs frequently (like every three months), but according to the spec sheet on these GE T5HO bulbs, they look to have over 95% lumen maintenance well after a year. (https://www.1000bulbs.com/pdf/ge-46699-specs.pdf) If it isn't loss of lumens, what drives the need to change bulbs so frequently?

[SantaMonica]

Experience

[piratefish]

Right at 3 months I will start to see HA growing on my rocks. You can try and let them go longer but keep and eye on your tank.

[SantaMonica]

I've also seen a graph where intensity starts dropping at 3 months. It occurs faster in a scrubber because of the 18 hours. In household use, at 9 hours a day, it would be 6 months.