Appears to be 40/ 3 hours right now for GPT-4 itself, between any way to use it.
I'm not calling it a comfortable cap 😛 I'm affected too.
"Would it be difficult for them to add this flexibility while we wait for more servers I wonder?" Yes, it probably would be intensely difficult.
GPTs are extremely different, potentially, than even the default ChatGPT-4, because they may have connection to actions, uploaded files, many functions like dall-e that GPT-3.5 doesn't have... and probably a lot of other 'behind the scenes' differences.
So, I recommend, if you want to continue a GPT conversation with 3.5, maybe during your wait time for more messages...
Perhaps yourself copy paste it to 3.5 and tell 3.5 you want to continue with it as best it can, please act as it sees the GPT in the log you shared.