I will agree. The high output T5 made such a difference when I switched! SO much brighter and with a dual (or quad like I use) fixture you can do the UVB and plant lights in one! The Arcadia fixture has a great reflector in it and this further intensifies the light. You can Easily use a 6% bulb in a 4' enclosure, but a 12% will work as well. If you have a very young panther I'd stick with the 6% and if it is too bright you can always add a piece of spare screen between it and the top of the enclosure (assuming its outside the cage). As for longevity, the bulbs will be good for at least a year! Arcadia is an awesome product.