program stops after approx 4hrs

The following is a global definition:

String dataString = "", Comma = ", "; // data to write to SD Card

I am attaching the full .ino but without reformatting. Is there an automatic way to reformat?
If I do that manually, I would be concerned about making many keying errors.

sketch_TimeSensorVac_170927.ino (8.88 KB)