I have just talked the old owner of the leo that i got for 500. He kept it in a 150 gallon tank and did only do a 25 % water change once a month! Just like the danish Hystrix breeder. Those leos and hystrixs are real hardy for sure!
There are a great many people that do water changes once a month. I am not one of them but if it works why change it. As long as you have adequate filtration and do not overfeed once a month water changes are fine.