When to change lighting and Kelvin question

I have T5's in my 29 gal. They are 7 months old. When should I change them?

14,000K has been recomended for my 90 gal. I prefer corals over fish but I like a more blue look. Is there a brand of light that is better or has the most bang for the buck? Where can I get the best buy on it? I currently have 400w of 10,000K

 

I also have 10k on my 90 gallon. Too yellow...yuck! After seeing sam's 15,000k halide, I recommend XM. oh, and ur t-5's should last til their about 12 months old, but i've gone longer!

 

Thanks

 

Might check these out...

http://www.marinedepot.com/lighting_flu ... mp-ap.html