...REALLY mean it.
I recently bought a pair of magnetless speed and cadence sensors to use with a G800 unit in one of my bikes. I liked it so much that I bought another pair to use in another bike that I own (the n + 1 thing). I keep all my bikes in the garage, including the first one with the magnetless sensors. Try as I could, the second pair of sensors would just not communicate with the G800 unit. Finally I took the first bike, the one that was already paired, and moved it inside the house, away from the garage. After I moved the first bike inside the house, the second bike paired with not problem.
Moral of the story: follow the 10M separation rule when pairing more than one set of sensors. ;)