white leds aside from their novelty are next to worthless ... I suspect a white fluorescent tube to last much longer than a white led
the phosphor rs in low-cost white leds are not high end, they'll wear out quickly. what you'll be left with is a dull blue led in a few thousand hours. not to mention the phosphor is very temperature sensitive and high ambient temperatures, operating or non-operating will degrade it further.
look at combining blue and yellow leds behind a diffuser for a basic white light source, or use rgb leds. Dichromatic leds (blue + yellow) have a pretty poor CRI, so if you're lighting stuff that needs to look good (retail product, food, etc), they'll do a piss-poor job of it, best off using RGB here.