If I only have to read 33 books on it to break even in greenness, then I can buy 3 new ones a year.
I've never thrown out an eReader. I've broken two and one I gave to a developer so he could work on some Kindle stuff. The other I sold on EBAY for parts. I gave my old Sony Pocket reader to a friend who is still using it. My other older Kindles are still here being used as back-ups - one is 3 years old. They all have displayed far beyond 33 books over their lifetimes.
Hey look at me being all environmentally friendly and everything!!!!!