[McNutty]

You've had multiple replies, but I think that one key piece of information missing from all of them is the fact that you could move between floating and fixed. In your example you might see rates going up and you'd decide to change from the floating rate to a fixed rate for a term of 1-5 years. A few years later you might go back to floating. You might also have your mortgage split up into 2 or 3 tranches with 1 floating and 1or2 fixed at different rates. You can move from floating to fixed at any time, but you can only from fixed to floating at the end of the fixed term (or earlier by paying the bank a break fee)