I just got off the phone with a good friend of mine who has a Civil 3D drawing with a large surface. Every time that he maneuvers around the drawing it takes too long to regen. Now we both believed he had a video card issue, but he’s under a deadline (of course, anything that can go wrong will go wrong near the end of a deadline). So until he can get a new video card we had to come up with a way to minimize the regen process.
So of course my brain starts cranking because I had to back, way back, behind all those cobwebs in my head and dust off an old friend. Some of you may already know this, but for you newbies, you may want to take not of the system variable REGENMODE:

That helped minimize the issue, but the it still took too long to regen. So we discovered a little setting that saved the day.
Apparently, he was drawing his contour labels and allowing his major and minor contours labels to be drawn, along with his contour label lines to be displayed as so:

He’d then go into the properties dialog box and control the masking and display of his contour labels.

It’s recommended that you control these setting with the label style rather than through the properties dialog box. We found that when setting the masking to “Contour Line Only” that’s when the lagging the drawing was most evident. Keep that set to “From Label Style.”
Also, don’t forget that you can layout our contour label lines and not have to deal with the display of the contour label line at all. Just go into the Settings tab and navigate to the to the “AddContourLabeling” command settings within the surface styles. Right-click on “AddContourLabeling” and select ”Edit Command Settings”:

In the “Edit Command Settings – AddContourLabeling” dialog box expand “Contour Labeling Defaults” and change the value of “Display Contour Label Line” from true to false:

You may want to change this setting in your template as well so you don’t have to do this for every drawing.