The WorkStar® 310/314 is warrantied for one year from the date of purchase. The warranty covers manufacturing defects. It does not cover "wear and tear".
For warranty issues see: Shipping & Returns Policy
No, the LED (light emitting diode) is a solid state device that does not "burn out". However, LEDs do get dimmer as they age. If left on continuously, the LED will start to dim after 10 years. The LED will not break in normal use.
Very tough — the WorkStar® 310/314 will survive a six foot drop onto a concrete floor.
Yes, they are rated IP67 = dust tight & waterproof to 3 ft (1 m), when the rubber USB cover is properly closed.