Curious I test my Pentax KX which is almost 40 years old and I believe older than the M4-P. I don't think it had ever gotten a CLA.

Shutter Test
Camera: Pentax KX
Serial : 8466143
Each speed was tested 10 times.
Speed Average Min Max
1 1.139860937 1.154734411 1.123595506
2 2.37699073 2.41021933 2.342468962
4 4.644250418 4.721435316 4.574565416
8 11.32502831 11.62790698 10.83423619
15 15.61524047 15.79778831 15.38461538
30 30.0003 30.3030303 29.63841138
60 57.3855159 57.83689994 57.20823799
125 113.481616 114.2857143 111.8568233
250 255.6498619 261.6431188 243.1906615
500 495.3928465 535.0454789 465.1162791
1000 933.0098899 1044.932079 878.7346221