I may replace the battery in my early 2011 MBP again because aside from not having a retina display it still does everything I want it to do and. My only complaint is it it a lot heavier than the current 15" models but since I don't travel much anymore except for a couple leisure trips a year I can deal with that for now.
As for recycling the old battery you may be able to drop it at the Apple Store or somewhere like Batteries Plus for recycling.