We tend to keep it to important stuff only that the entire company needs to hear. But this past week we had a standup where everyone was supposed to answer a question (I forget what) and we did it in 10-12 minutes. We've been practicing for a long time, many of us come prepared. But even when everyone was expected to say what they were doing that day, we still averaged 10-15 minutes with 70 people. Just come prepared, don't dilly-dally.

Guessing it's not really a "standup" where 70 people give status, but just that you discuss blockers/issues relevant to a team that big.

I hate standups that are just status updates, that's what the board (Kanban or scrum) is for, if you don't have anything interesting or blockers to raise just say "pass" and save us all