I have a sun leaves t5 4 foot strip light, I got it in jan sense then it has run fine no problems. well I called the place I got it from and they told me to change the bulbs every 6 months to a year. So far it turns on no problems.

I talked with a staff she thinks they are trying to get money from me do you think its true or do I need to buy new replacement bulbs.

Alex, fluorescent tubes degrade over time, producing less and less light intensity (lumens). They will also burn out, but that might take several years. The only true way to know when to replace tubes is by purchasing a light meter and see what the lumen output is 6", 12", and 24" away from the fixture. You really need to do that when the tubes are new though. If you do it after 6 months, degradation will have already taken place. But at least by taking a reading now, and then every few months, you will know what the amount of lumen-change there is during a specific span of time. You want your fixture to produce at least 8000 lumens, but that's predicated on having a four tube fixture. I have six-tube fixtures, and they are T-5H tubes, producing 32,000 lumens 6" from the fixture. You won't get anywhere near that output with T-5 tubes.