Everyone settles into their own routine, of course. However, everything I've read and from my own experience, it is much better to changle 10-15% of the water every week than to wait a month and change 67%. It maintains more stable conditions.
Each method has their good and bad points. These are the things I don't like about frequent water changes
Water changes can be stressful on fish. We have one fish, who for the first 8-10yrs (yes we had him for almost 13 years) would knock himself out by running into the tank whenever something came into the tank (ie a siphon, hand, new plants even). Thanks to him I learned that you can do chest compressions on a fish LOL.
One way that fish "grow to the size of the tank" is by releasing a hormone into the water. The lower the hormone level the larger they will grow. Fish breeders will usually change water of en to stimulate growth in baby fish (the bigger the fish the more they can charge for it).
This effect also regulates spawning. If you are trying to encourage breeding, then frequent water changes are a good thing, but it too can stress the fish out.
Another problem can be the stress on the tank itself. With the amount you are talking it isn't likely... but when a large amount of water is removed and added back in it can stress the seams in the tank. IMHO one of the biggest mistakes people make is to use a bucket to refill the tank. That can add a lot of stress to the seams. It is better to use a hose to fill the tank.
Of course infrequent water changes has its draw back too. The biggest I run into is algae. I try to keep algae eaters in the tank but our tinfoil barbs keep eating them. Looks like it is time to get another apple snail.
Another problem with infrequent changes is if someone changes the water and filter material at the same time. Natural good bacteria that grows (such as in the sponge you mentioned, which we use. It will also grown under an under gravel filter which we also use) helps keep the levels stable. If the water and material are changed each time on a 1X per month schedule, then the good bacteria population is destroyed or at least brought down to dangerous levels. This is especially true when there isn't an under gravel filter. This results in large fluctuations in levels, or in the worst cases, the levels will slowly become worse because of the lack of good bacteria.
IMHO the best way to start up a tank is too buy everything you need except the fish. Set up the tank and let it run for a min of 2 weeks. You can buy small bottles of the good bacteria to help jumpstart the biological filter process, but it still a good idea to let things run for 2 weeks. This also allows time to make sure non of the equipment is defective.
The good bacteria is also good to add to an established tank after treatment for any diseases. Often the treatment will kill the good bacteria too. One way I've found around that is to use the medicated foods, instead of something that goes directly into the water. I like to give the medicated food for 10 days afer introduction new fish. However If I had the room, it would be better to have a quarintine tank for the new fish and feed just that fish the med food.