The MBP is about 3 years old; RAM is already at max and I did a DIY HDD upgrade about 6 months back and swapped the old HDD for a new 320Gb one.
I use it on the coffee table in front of the TV and use it most of the time. The Mini is/was upstairs in the study, but I only use it when I need the big screen, the desk space and the extra storage space etc.