How often should you change t-5 bulbs? led strips?

[Jeppeterpan]

I had 2 kessil 150 ocean blues on my 72 gallon and I'm doing a led vs t-5 experiment on color and growth. Now I have a Current 48" in 54wX8 bulb t-5 fixture and was wondering how often should you change bulbs? Right now they are on a schedule in which blues come on at 6:00pm. Whites at 7:00pm. Whites off at 1am. Blues off at 2am. Let me know what you guys think? Also, any recommendations on a led retrofit to run w t-5 besides reefbrite strips? I would like to run 2 strips for shimmer effect. Let me know what you think? Thanks guys!