An Empathy Session can be a week long. And our users get wrapped up in their day to day and it is easy to forget about the session. I have been manually creating google labels for group emails to remind them a couple of times during the week.
"Thanks for the participation. Getting some great ideas. This is a reminder to jump in and give us your opinion on <subject is being discussed>. Reminder - the session lasts until xx/xx at xxpm'
I always get engagement after sending one. But is it real pain to manually create this 'nudge' email when everything I need is in Aha - other than the option! Including a link to the session is also important. And allow the message to be customized!