I think about 3 weeks. I've had them for nearly 4 weeks now and the biggest change now was the promised GroverHuffman Pharoah ICs. That took my system to High End land this weekend after breaking them in. Combining the two, I don't feel the need to upgrade to $60K speakers from my Legacy Focus. I'm sorry that the E-Mats do cost a lot (4X that of the ICs) but they are not bling, but the real thing-great!
Another apparent benefit of the E-Mats, I haven't had one day or time of day where I thought the system was not sounding great. Installing a Bryston BIT-20 three years ago eliminated most of the problem but the E-Mats appear to have totally eliminated that problem.
Have others experienced a cessation of daily sound quality fluctuations as well?