I've been using Focal Clear MG Professional for 1,5 year day by day. First of all, these headphones are the best of the bests in sound, at least for me. Music never sounded so natural and detailed like in these headphones. You can recognize every nuances that you adjust in a mix when you wear them. When everything sounds the most balanced both in volume and in tonal sense in these headphones, then your mix will be killer and so natural.
One thing that's bothering me is when I pick it up I feel that it will fall apart immediately. When the two speakers don't align perfectly and the headphones get a little twist, it feels it will break. Fortunately they don't break but it's an unexpected feeling from such an expensive headphones.
The other thing is that the red leather surfaces are very sensitive, they can get messy and dirty easily if you wear them day by day. The manufacturer gives an extra pair of ear cover foam in the package but the head bound also has this leather material which stays messy anyway.
But if you don't use them every day for hours and hours, probably it won't be a problem for several years.