How often are ap_periph firmwares released?

Hello. I use matek l431 devices to convert a rangefinder and a proximity sensor to dronecan. They work great.
I am using the firmwares from the “stable” folder in the tree. I.e., ArduPilot firmware : /AP_Periph/stable/MatekL431-Rangefinder

That firmware is about a year old. I also see a latest and beta folders which look like they are probably just daily builds.

I was curious what the release cadence is of ap_periph firmwares and if stable is what I should be using? What triggers updates and releases of the ap_periph firmwares? Is it ok to be using the stable ap_periph firmwares with arducopter 4.6 beta, or should I update my ap_periph firmwares to the latest folder as well? Thanks!