Supposedly, ALL Ceramic bio-media's clog eventually(due to mineralization), or so I've heard discussed as of late.
I will admit however that I AM a proponent of and use both Substrat Pro, Matrix, and Matrix pond. In addition, I ALSO use pot scrubbers, and in some of my canisters swapped out the Matrix and Substrat Pro due to the fact that you can ALWAYS clear the pores of the Pot Scubbers with a good rinse with the garden hose(dont do it all at once if it's your PRIMARY BIO however).
My thoughts as far as clearing (or attempting to clear) the pores on matrix and Substrat pro have been to clean small batches (1ltr) once every 8-12 months by soaking in 50/50 bleach and water for a few days, then rinse, and soak in heavily dechlorinated water for a week. Then put back into operation.
This last time however, I DID-NOT put the Matrix and Substrat Pro back yet, and it's been 2 months. I've just been letting the srubbies do the bio, and have experienced no spikes at all.
As I've said once before, I believe A LOT of us (I know I DO/HAVE)tend to use waay more bio media than we really need. I'm fortunate to have 7 light to medium stocked tanks however, and do 50% water changes each week, and use 2-4 times the amount of purigen recommended on each of my 7 tanks.
My opinions and experiences only, your mileage may vary.....