I ended up getting the whisper 10-20 gallon for my tank, intending to use it after the tank has cycled.
However, I do know that pads need to be changed and I am not sure how to do that without it needing to be cycled again to cultivate bacteria.

I think I have heard of people dipping the new one in a bucket full of water from a water change, but is that enough for it to get the bacteria?
I was thinking of maybe putting two of the pads in at once (the old and the new together). Would this work?

Also, I believe I heard somewhere to let your filter stay in the tank until it is pretty used up/torn. Is this a good idea?