We do replace faculty computers every 4 years if possible. However, we tend to pass the older computers down to other areas if they are still usable, which we are not able to do. We do have a lot of Mac's in the College. I'm actually really pissed at Apple for no longer allowing to use iMac's as external displays. We have a lot of 27" iMac's that wont be usable in the near future once Apple stops supporting Intel based computers. I'd love to be able to use the iMac's as external displays since they are great 5K monitors.