I think what he is looking for is a concrete explanation of WHY water gets bad in the first 30 days, the logic being that if you eliminate the cause, you could eliminate the need to change water.
If I understand it right, it is multifactorial, but the cumulative effect is water that is just better to replace than to try to fix. Factors include:
1. Over use of chemicals trying to micromanage water balance
2. Sometimes a poor understanding of "sanitation" versus "balance"- so not only overuse of chems, but inappropriate use
3. Probably more use in the first month or so b/c it is a new toy
4. Purging of any chems/debris sitting in pipes, etc from the warehouse
5. Skin pores that may not be as clean as you like to think that they are- unleashing all their contents in your water
By that logic, someone used to tub ownership but just getting a new tub MIGHT have fewer problems than a total newbie, but since some things are not a matter of experience, the general trend is that everyone dumps after 30 days, if they follow Chas' advice.
I did!!!!!