I appreciate your input. Honestly, our goal was 15 minutes, but we weren't able to remove certain measures. We're actually not getting much drop-off at all!

Edit: I'll also note that a lot of studies run this long. It just depends on whether it's recurrent and what the incentives are. For us, it's a one-time survey, but we weren't able to get as many incentives as we wanted from our department, which would have made it easier.