Hi Jody. I do provide extra content for my backers. It is labeled Behind the Scenes content (BtS for short). All of my backers receive this and it is backer only content. It may be extra blog posts (delivered via Patreon). I also have done photos, video, and audio.
Sometimes I’ll leave the recording running after my episode officially ends and will share that extra audio with my backers. The key there is to let any guests/co-hosts know you do this before you do it. They may not be wild about it if they think they’re having a private chat with you only to find out later that it wasn’t private after all.
One thing I do if I wish to offer extra audio is to record myself giving some extra insight into the episode. To do this I most often use my iPhone 6s. There are several apps one can use to do that. Have been known to record myself while walking, sitting in the car, or commuting (naturally only when someone else drives).
My backers like to receive insight into how an episode is recorded, who the guests are, things I may not be able to share with a wider audience, advanced info, etc.
Once that extra content is created I release it to my backers through Patreon. The audio file can be attached to the Patreon post so that backers will receive it when they open their e-mail notification.
As to length that becomes trickier. It really depends on whether you are providing video or audio. Video should be much shorter perhaps 5 minutes long as most although 1 or 2 minutes is more ideal.
For audio I think you could go longer. Let’s pretend your show is 1 hour long. A 10 or even 15 minute audio recording is likely the max you’d want to do. Longer than that and you almost have enough content for another normal episode.
One thing in which you may be interested is knowing that I’ve had several backers become backers because of my behind the scenes content. They said my doing that along with a couple other things I provide to all backers made them want to become backers. They felt all of this provided a lot more value to them.
One of my mottos is to give more than I receive. If a backer is giving me $1 each month I want to give them $3 or $5 worth of content for that dollar.