I would think that if you turn the pumps off for a few hours it wouldn't be too bad. I'm OK with cleaning it out once a year or so but if it's more than that it may be more than I'm really looking for. Does the sand stay on top of the mud? Does it settle? If it stays on top I could just siphon off the sand and reuse it.
Here's the stuff I use, I replace 1/2 of it every 6 months.
http://www.ecosystemaquarium.com/products/eco-marine/miracle-mud.html