My late 2012 Mini is still working well but seems to be slowing down a tad even though I run Disk Utility and Clean My Mac on it every so often. I've also disabled a few of the start up items to try to speed booting up. This coming week I'm taking it in to have a solid state drive installed. He will migrate everything from the current drive to the new one. But I do have a CCC backup on another 2TB USB drive if needed.
I already have 10GB out of a possible 16 max for RAM and I'm told the new drive should speed things up nicely with the current RAM. Parts and labor is just a shade under $200. That'll buy me a few more years of use before I shell out $1100 or more for another Mini.