Very nice. For 3 months, that's very pretty solid amount of print time - about 75% uptime. It's cool to hear about people turning this hobby into a business and being able to sell things.
I also have about 3 months of print time on my build. It's not a MK4 though. You have more print time on yours, but but in terms of m/day I think I have you beat.
I'm guessing you print slower and/or with narrower extrusion widths? I haven't bothered swapping my 0.4mm nozzle for something chunkier yet, but I usually print with 0.2mm layers and 0.6mm wide extrusions with speeds between 70 and 100 mm/s depending on feature type.