It would be extremely helpful for users to have multiple voicemails saved that they can have for specific clients, but especially as an out of office temporary voicemail. They can then set the out of office voicemail to run for a specific time period while on vacation without having to re-record or re-save another voicemail.
One a side note, it would also be cool to cater your voicemails to your different lines of business. For instance, I'm insurance, and would love to have a different voicemail for my Life Insurance clients than my Medicare clients.