With the new fans installed in both units I am logging the CAL 72 values daily.
Date/time 3458A serial 5XXX 3458A serial 4XX
Day 0, Dec 30, 19:00 .989773311 32.1C .988870057 31.4C
Day 1, Dec 31, 19:00 .989773289 32.2C .988870101 31.5C
Day 2, Jan 1, 19:00 .989773232 32.2C .988869970 31.6C
Day 3, Jan 2, 19:00 .989773424 32.2C .988870044 31.7C
Day 4, Jan 3, 19:00 .989773419 32.5C .988869978 32.1C
Day 5, Jan 4, 19:00 .989773351 32.2C .988869669 31.8C
Day 6, Jan 5, 19:00 .989773242 31.5C .988869148 31.0C
Day 7, Jan 6, 19:00 .989773382 31.9C .988869253 31.5C
Total PPM shift 0.010 PPM/day 0.116 PPM/day