I use my big mat daily. I do rotate my mats and turn them over occasionally. I prefer the solid side because I find the grid distracting for most cutting, so that side does tend to wear out faster. I use a scrubbie crocheted of nylon netting to clean my mat. Works better than anything else I've tried to get those teeny bits of thread that embed in the mat. I admit I probably don't change my blades as often a I should, although I do sharpen them frequently. I have worn through two smaller Olfa mats in about 3 or 4 years each. One of them I blame cutting felt. Right now I'm using one of those one-sided blue mats that isn't the self-healing kind because they cost less to replace. But I think it's harder on the blades than the softer ones. It's kind of a catch 22: Change your blade, save your mat. Change your mat, save your blade. Both are expensive.
And will someone please explain about the soaking? That is one thing I've never heard about.