Yep.
There are many voters who use absentee ballots and mail them in as soon as they get them.
Then, a week or so before the election, something comes out about their candidate that makes them wish they could change their vote.
Another point against mail-in voting.
If we go to an all-mail-in system for all elections, then the states have effectively told the candidates to spend their campaign time and money earlier and to not bother campaigning within 3-5 days of the election. Any ads that run after a ballot could be mailed in time to be counted would be wasted. In effect, the election would be held 3 days before the official polling dates. We just wouldn't have the results as quicklly.
I'm of the mindset that, if you haven't made up your mind who to vote for before election day, chances are good your vote won't be well-informed or rational. My mom used to wait to see who the polls said were ahead and voted for those candidates. Her rationale was, "The majority knows more about who to vote for than I do." She probably just wanted to feel good about having voted for the winner. Just one more reason for everyone to ignore the polls, especially when we know most polls nowadays are so biased and skewed.
Polls are not designed to measure public opinion. Polls are designed to shape public opinion.