The newer AutoCADs tend to chew up a lot of graphical memory for all the WOW factor visual effects. Try looking into your graphics card acceleration, and possibly turning off some of the visual bells and whistles if you don't need them. A big complaint is the Layer Properties Manager palette, and a lot of people have found immediate performance improvements once they switch back to the classic dialog box. The command is CLASSICLAYER.
As for slow saves, in my own experience I found the SAVEFIDELITY system variable to be the culprit behind extremely long saves. When turned on, which is the default setting, it will translate annotation objects into multiple copies in different scales and on different layers, for users of 2007 or older platforms. It also translates them back into a single object with many layer states again. This takes time. I went from 5 minute saves down to 13 second saves when I shut mine off. I also read a similar post yesterday with the same solution and it worked. If you have no users of 2007 or older in your office anymore, set that to zero. You can still save down to 2007, and just keep in mind if you deal with outside users with 2007 or older, you can always turn it back on just for saving and sending them your work. I hope this helped!
I hope my info was useful, but if by some odd chance it actually solved your issue, feel free to mark your post as "Accept as Solution". Thanks! 🙂