The user has to click the button though to fire the event because otherwise when would Twitch send an event? Another service (not mentioning names, not sure if that is allowed or not in these forums) can send an auto-renew list, which I believe they say runs at midnight (forgot which time zone), and that may not be good for your chat as it contains every re-subscription, which, could be tens, hundreds, perhaps thousands of entries. I am not sure why a bot would miss a PM though, as long as it captures all of the PMs and has them in a queue, wouldn’t it get processed in that queue?
If there was a wish list, I would really like to see what another service has with a websocket service that you just sit and listen on for any updates. It makes it very nice in the case of new and returning subscribers as you aren’t required to constantly hit a webservice but just listen on a socket for a JSON payload. I am sure that would be a hit to infrastructure and bandwidth, but not sure if it is any worse than people hammering the subscription API constantly.