Empirical evidence would suggest that they didn't consider it to be such.
Show me where that happened to Lil' Tommy. Who did he make a mutual promise with?
Whoever else pledged to hold himself to term limits, but reneged. Since the people of his district didn't mind, the only other people who would would be his adversaries, who might have been counting on seeing him leave. But since they also didn't hold up their end, they had no right to any legitimate expectation of that from him.
Just like Clintoon. Nice company he's keeping, eh?
Whoever else pledged to hold himself to term limits, but reneged.
LOL. Damn you, Mister X! Damn you to hell, for making such a good man break his word!