As a negative to the aged bio-filter media, this simply may not be possible for a new aquarium owner who has no friends to obtain aged filter media or if one does not trust a Fish Stores (or even a friend) aquarium health for obtaining aged/seasoned filter media. In this case, I would recommend one of the next two methods.
Further seasoned media cycling method tips
An ammonia spike is not uncommon with the use of seasoned media for there to be an ammonia spike when more fish are added, often this spike may take a several days depending on the amount of fish added as well as the bio load that the seasoned media has grown to handle.
Generally this is not too much of a concern, but the use of Prime, cutting back on feeding, and definitely placing the addition of any other fish "on hold" until the nitrifying bacteria "catch up" with the new bio load are good practices.
As an example of what happens (and this is NOT scientific, just an analogy):
If say you added a sponge filter from a 20 gallon tank that is fully seeded to another 20 gallon tank that is brand new or restarted after bleaching.
This seasoned Sponge filter for the sake of argument carried 50% of the bio load (assuming another exact filter), in theory you could only stock this new tank to 50%.
If the seasoned filter only carried 25% of the bio load from the tank it was removed from, then you could only initially stock the new tank to 25% initially.
I should note that with the use of seasoned filter media, generally the nitrifying filter media will quickly colonize the rest of the tank, so waiting 6-8 weeks to add more fish is rarely necessary (at least I have never observed this in many trials using seasoned filter media).
Fishless cycling avoids both of these problems by providing ammonia for the bacteria without the need to buy any fish. Once the aquarium is cycled, you’re free to add whatever fish species you want.
Information to help you in Cycling an Aquarium
The only concern I have is with outlining any particular type of water change schedule. People tend to see what they want and forget what they don't...and 2x 50% per week I have a feeling will become the standard advice given (despite the very clear disclaimers you included). I'm a big believer in letting your test kit dictate when water changes need to be done, not using a clock or a calendar. Since fish have different bio-loads and different phases of a cycle present more risk than others...I think it's important to always know what's happening in your aquarium.
Fish-in Cycling: Step over into the dark side
To understand when your aquarium is ready to add fish and what you should do if you’ve already introduced them, it’s important to know what the nitrogen cycle is first. Keep reading for more info on the nitrogen cycle or .
Starting The Aquarium Nitrogen Cycle - Cycling Without Fish