Sorry to hear of your cold. Get well soon.
Of course the rule is always the activator does what he (or she) wishes to do. This is especially important for safety reasons at this time of year! You may find that in summer stations stick around a bit longer on each band as they’re also enjoying the view and the sunshine.
The fact that a chaser is not located actually at his/her station but is monitoring SOTAWatch via a smartphone does add the problem but is, honestly, not something the activator will have high on his list of priorities.
As you quite correctly noted, weather can be a big factor. Last Thursday at Auerberg, an easy access summit but still bitterly cold, I worked 48 stations in 30 minutes, but it felt like 2 hours in the temperature I was in. (no bothy bag here - but it might be a good idea in minus 10 degrees!). I could have just worked the first 5 or 6 and then packed up and left but I didn’t.
Another thing that can cause an activator to shift bands (or at least frequency within a band) is when another amateur comes on, or very near to, the activators frequency and starts calling CQ or calling his mate without even checking if the frequency is in use. Unfortunately this is happening more and more and not just in situations where the DQRMer can claim to not have heard me - as other stations near him have given me true 5-9+15dB reports (I run a bit of power from summits sometimes…).
What I have started trying to do is notify chasers of when I plan to be active from the summit. Often this will be 20-30 minutes before I call CQ. Of course that spot can’t give an accurate frequency but at least you know to be back in your shack ready for when the “real” spot comes in.
Something else - if an activator is spotted by someone else he or she could already have been on that band from the summit for 30 minutes (with no cell phone coverage) and so after working the person who spotted him/her may decide it’s time to try a different band as no one is coming back to his CQ calls any more.
The spotting system is great when you have access to it from a summit! It makes the activators life a LOT easier! After sending a spot and seeing it come up on SOTAWatch, I will normally have at least one person calling me within the next 30 seconds! SOTAWatch doesn’t need 15/20 minutes to work its magic - nearer to 15/20 seconds!
A solution that you may want to look into, if you are so inclined, is to run your rig remotely from your smartphone. There is a fantastic free (or $5 without Ads) app called PocketRxTx which can enable this for a whole range of rigs (over WiFi, USB or Bluetooth) - I actually use it as an activator to get a large readable screen on my portable rig as the small 2" OLED screen is totally unreadable in sunlight. If you set this up you’d be able to stay wherever you are when you see the SOTAWatch spot and call the activator. (send me a reflector PM (Private message) if you are interested in trying this out - the Smartphone has to run Android though - this software is not available for iPhones).