Event Duration is available in the events table control in Axiom and in the event pull in Canary's Excel Add-In. We didn't find a way right off though to include the event duration in an end event email UNLESS we made it an event property. That works, but requires a minor amount of extra setup, and more important, it means that if we use an event table in Axiom and want to include event properties because of other properties we have setup there, we end up getting the duration in properties even though we don't need it there. Is this the best setup we can use currently or is it possible to include event duration in the end event email but I'm missing it?

The event email template instructions just say: 

Values inside of "{{ }}" are placeholders and will be replaced with their values when the email is sent. Valid placeholders include EventTypeName, EventStartTime, EventAssetPath, and EventDescription. Calculation variables can also be used as placeholders, for example "{{tag1}}". Event property values can be used in the "Event end" email.

and don't mention EventDuration as a placeholder option. 

We could put EventStartTime in the end event email but then one would have to subtract start from end in their head to get duration verses it just being directly given in the email.