Not riding more then 45 mins at a time (typically 20 mins). I'm also a fair beginner with less then perfect riding position, not a great seat, out of shape and overweight. I can post nicely tho :)
My stirrups are at least 5 yrs old but have maybe 6 months of riding actually on them as I took at 5 year hiatus from riding.
I'm wondering if I should try something different - maybe just an offset, no jointed or perhaps another brand like Herm Sprenger's 4F system which has the same features as the MDC.