Calendar event later described in a post about the event

How do you suggest using calendar events when the event is later described in an ordinary post?

I am considering doing this:

Create an advertisement calendar event (calendar post) with URL like
URL = bze.org.au/event/community-radio-show-10-july-2017

After the event we could use a plugin like “Post Type Switcher” to change the “calendar post” to an ordinary post which has a brief description of the show and a link to the podcast, our “podcast post”.

. In changing the event post to the “podcast post” the URL loses the /event/ part of the URL, so the “podcast post” it gets a new URL, say
. URL = bze.org.au/podcast-community-radio-show-10-july-2017
. This has the potential to generate broken links, but few people would store the calendar post URL, try to link to the destroyed URL and so find nothing.

This process avoids having two posts about the radio show: (1) the calendar post and (2) the podcast post. So:
. the web site stays smaller
. the web site has less duplicate content
. After the radio show, Google searches for the show guest “Fred Jones” would find the “podcast post” and not the “calendar post”. They would see the option to hear the show.

What do you recommend for this?