In Germany there was a campaign promise of the SPD at the last election to not change the current law of accepting refugees.

The SPD broke that promise when the amount of refugee seekers rose drastically. I think that fact that they did so, shows that they react intelligently to changing circumstances. I wouldn't want to have politicians looked into 4-year promises that prevent them from acting dynamically.

Binding promises also make consensus finding harder and could even forbid it when the promises made before the election aren't compatible.