poll-duplicates

Which of the following strategies should I enact to attempt to reduce the frequency of duplicated polls?

• There's a system that checks if a poll has already been sent before sending it again, but it clearly doesn't work super well so try to fix that7
• Make the polls send earlier, like 7:30-8:30am, so they have to be in the night before otherwise we're almost guaranteed to have a duplicate
• Make the polls send later, like 5:30-6:30pm, so there's more time day of to prepare a poll
• Sit down today and prepare the next two weeks of polls, then next Monday prepare another week's worth so that we're always at least a week ahead4