Well almost... I swap my plug pretty regularly so it will always be fresh. To freshen up a plug and make it new again, I use a pneumatic spark plug cleaner from Harbor Freight Tools (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=32860).
I learned this trick back when I was a kid hanging around 'real' mechanic shops. I two or three second blast and my oily plug looked like brand new! The plug cleaner can make a fouled plug work again, and older plugs can be kept in the toolbox or fanny pack as an emergency spare for your bike or someone else's.