The email I got spells out some provisions for refusing extensions and junior mans, (x number a month, y a year,) and with reserve rules in there as well to assure that all reserves are tapped in and out of base before an extension happens.

So if you really can't be extended on that day, you have protection for refusing it.

Extensions need to be a possibility. There are times when reasonable planning doesn't even cover a situation, in which case, I feel like scheduling should be able to try to find a pilot willing to do the open flying. The issue has been that the planning hasn't been reasonable, and the pilots haven't been willing.

"You've been extended..."
"What about hot reserves?"
"We didn't have any today..."
"I can't, I have my wedding to go to, can you find somebody else?"
"Missed trip!"

vs.

"We have a turn that needs to be covered while a home reserve gets to the airport, we used all of our hot reserves because of crews stuck in the biggest blizzard in years. Can you do it for some additional cash?"
"No, I'm getting married today."
"Ok, we'll call the next guy and offer him some extra pay."