I think I speak for everyone in the Minecraft realm community by saying that when you pay 7 dollars for a server, you should be able to afk whenever you desire.
This is a recurring issue in realms, you can only leave your character idle for 15 minutes before being kicked from your own server.
This report is invalid as this appears to be a Feature Request and not an actual issue within the game. If you wish to suggest or share your ideas, please do not do so on the bug tracker, as this place is specifically used for tracking and handling bugs. However, here are the appropriate environments in which you can share your ideas.
Official Minecraft Feedback Page - https://feedback.minecraft.net/hc/en-us
Minecraft Suggestions Reddit - https://www.reddit.com/r/minecraftsuggestions