This piano is a big old upright with a scale as long as a six foot grand.
With the swamp cooler running, the temperature was 72 degrees. I turned the cooler off and measured the pitch (one string) of D2, D3, D4, D5, D6. Temperature 73 degrees. Then I opened the door. Here are the results.

About 1 1/2 hours later, Temp 80 degrees. Pitch change in cents.
D2 -1.5, D3 -4.1, D4 -3.9, D5 -3.8, D6 -2.3

The bass only changed 1/3 as much as the tenor. There was a .2 cent widening of the octave D3-D4.

All pitches returned to original readings when cooler was turned back on.

kpiano

Amazing, just goes

Sorry, hit the wrong button.
I tuned a 1923 Heintzman 6'today. It resides in a 200 year old house. The owner told me to simply come every two months from now on. As the sun was coming down in the west through many windows, I could feel the temperature rising, and my tuning shifting.
If pianists had their piano tuned every week, we would not have time to post here.We would be rich.
Tune the piano when it is in it's most frequent state and hope for the best. What you said about pitches returning to normal when the cooler was turned back on is a good testimony of your tuning stability. Knowing how to set the pin is key, and your measurements prove how YOU can achieve that goal. Good for you.
The bass never shifts as much because the bridge is closer to the rim, therefore does not move/swell/increase bearing as much.
What do you use for pitch measurments?

I used a SAT I.

I think I need to get the piano muted right away and lay a center string tuning on the whole piano while the temperature is still cool. Even if it's a few degrees warmer than the temperature in the evening between the black stage in the sun all day and the lights and crowd heat (15,000 people), it should be a couple of degrees warmer on stage. Then I can do unison tunings even as the piano goes flat. I just don't want to do any aural checks of the octaves because the temperature will be changing 5 degrees an hour. If the piano is at tension, one pass at 80 degrees will be my guesstimate.

kpiano