The Mishnah in Peah and in Davening in the morning for those who say Korbanot we list Mitzvot which have no shiur (limitations) it seems one important one is missing we say in the Haggadah "Kol Hamarbeh LIsapir Byitziyas MitzRayim Haray Zeh Mishoebach". Therein we have another mitzvah which has no limitation yet it is not Listed why is that?
"Kol Hamarbeh Lisapir Byitziyas MitzRayim Haray Zeh Mishoebach" means that when extending the time past the end of the zman, one is to be praised even though one is no longer fulfilling the mitzvah. Note that the story has Rabbi Elazar ben Azaryah continuing to speak of Yetzias Mitzraim past chatzos even though he held that the seder had to end at chatzos. Thus, this mitzvah is not one of the ones that "ain lahem shiur" appilies to. Those mitzvos have no minimum and no maximum. This mitzvah is no longer commanded past the end of the zman (though someone learning more does get praised).