Pieter's tank is also over 2000 gallons (when you calculate all connected systems), with 1,000 kg of live rock, and a very, very large fluidized bed filter. The majority of his bacteria likely reside in the LR and the bed filter (which has fine grains, much like sand, and can act as a repository), not necessarily in the sand. Assuming your tank is not like this and like most tanks... much of your bacteria will live in the sand, and disturbing them is going to cause more of an upheavel than in his. Some people believe that deep sand beds can have a finite "lifespan" and will eventually accumulate too many nutrients to be sustained, but even this theory is on the scale of years (and this is controversial at best, there are also people who do not see these results in a stable DSB held for over a decade). In the average tank, regularly changing out or disturbing the sand bed (unless it is a very, very SSB that is just there for looks) is going to cause a lot of instability and can risk causing a crash from the nutrient release alone, and never would allow proper establishment of any bacteria. Remember clean-looking does not always = clean water. I'd much rather have good water parameters and a little bit of black and green below the surface; I think it's neat to watch the worms and other life below, also.