House rules establish the minimum length for a voting period as 15 minutes. There is no maximum period specified. Anything beyond 15 minutes is at the total discretion of the majority leadership. The leaders may signal the Chair to announce the results promptly at the end of 15 minutes, or hold votes open longer, as they wish. The minimum period was established to protect Members' ability to get to the floor on time, scattered as they are among 3 office buildings. The countdown clock tells Members how much time they have left to guarantee being recorded. Once the clock reaches "0", Members know they are at the mercy of the Chair's call.

Missed votes reduce a Member's attendance rating and the percentage of missed votes often becomes an issue during re-election campaigns. Nothing upsets Members more than missing a vote, so the leadership tries to be flexible. However, if the vote is very close and the results are favorable to the majority party, the decision is often to finalize the outcome rather than risk losing the proposition by appeasing late or missing Members. Even after the electronic voting machinery has been shut down, the long-standing House practice is not to announce a vote as long as there are Members in the chamber still seeking to be recorded. It seems there are always 2 or 3 Members who dash in at the moment the gavel is coming down. You will hear Members on the floor shouting, "Vote, Vote" to alert the Chair that another voter has entered the chamber. The late-comers must approach the rostrum and have their votes recorded manually by the tally clerk.

Factors the majority leadership take into consideration on when to close down a vote are (1) whether party whips need extra time to persuade recalcitrant or undecided Members how to vote; (2) to allow Members who have called to say they are not on the "Hill" time to get back to the Capitol, or (3) to try to track down MIA (missing in action) Members if their votes are needed to change the outcome.

Members may change their vote as often as they wish during the open voting period. However, during the last five minutes of a 15-minute voting period, or after the electronic voting stations have been shut down, changing one's vote must be done at the rostrum, by handing in a signed card (green for yea; red for nay) to the tally clerk. So, when the Chair announces the final vote it is a compilation of 3 lists: the electronic machine count, the last-minute Members who were recorded manually, and those who changed their votes at the rostrum. Votes changed manually are recorded in the Congressional Record and are published right after the vote tally. However, votes changed by electronic device during the open voting period are not noted.

The Senate has also agreed to a 15-minute minimum voting period, with no established maximum. While the average vote in the House takes about 18 minutes, the Senate takes an average of 23. Without electronic voting machinery in that chamber, Senators either respond orally with "yea" or "nay" as the clerk reads their name, or they approach the well and signal the clerk on a first come, first served basis. Senate leaders express constant frustration at the slow pace with which Senators arrive in the chamber to vote. With the smaller size of the Senate, every vote counts and the leaders are often forced to wait for dawdling Senators in order not to change the results. Every so often the exasperation builds, and you will hear the Majority Leader lecture his colleagues on the floor, threatening to shut down the vote, no matter what, at the end of 15 minutes. Even though he usually gets applause from those on the floor who are also tired of waiting around, he doesn't make good on the threat. As in the House, attendance ratings are electoral issues and close votes necessitate accommodating Senators if their votes are needed ones.