The record length is one minute.
In Instagram there’s a new tool that allows you to exchange voice messages in Direct.
To record a voice message have to hold down the microphone button next to the window typing.
Maximum recording length is one minute, and listen to it a few times since the voice message does not disappear from history.
As writes TechCrunch, with the new feature, Instagram will be able to compete with the messengers Viber, Telegram, Facebook Messenger and WhatsApp.