I used to turn it off if I was tracking and experiencing latency.
Then I realised that it was always the same plug ins causing it. Either look ahead plugs like the CL, or CPU intensive ones like Perfect Space. The LP64 plugs were another.
Now, I simply disable those specific plugs if I run into problems, and all is fine, so no need to disable PDC.
Remember, when the button is lit, PDC is disabled on live input tracks, when it is grey, it is enabled.