Assuming I bring enough batteries. Because I am selling something at a pushcart and I need the light to shine on my product. Will the bulb spoil easily?
Yes. That would be fine. You should get thousands of hours out of an LED. If I were you I'd use rechargeable eneloop batteries, and I wouldn't run the light on max all the time...heat could become an issue.
Yes you can. I've got a quark AA, and on high with a Li-on it draws around 1A. If you check Cree's lumen maintenance results here http://www.cree.com/~/media/Files/C...Lamp/XLamp Application Notes/LM80_Results.pdf
A XP-G driven at 1A at a reasonable junction temperature of 85 degrees C lost only 1% of its output after 6000 hours of testing. Estimated lifetimes for the loss of 30% of its output is around 60 500 hours. And don't forget, that's at 1A, with an alkaline the current is much lower and you should get at least 100 000 hours before any noticeable dip in output. At 10 hours a day, thats 30 years...