This value reports the average duration, in seconds, of the voicemail messages currently stored across the system. An admin can use this figure to judge whether callers are typically leaving short quick notes or long messages, which affects how quickly cueMessageTimeUsed will grow as cueMessageCount increases. If cueAverageMessageLength suddenly grows from 30 seconds to 3 minutes, the admin might investigate whether a particular mailbox is receiving unusually long voicemails, perhaps due to a caller repeatedly failing to end a message.