Informed Webmaster

Do you use the "auto updating" of plugins these days?

If yes, do you decide to take backups of the WordPress install? I would always take a backup of everything with every WordPress update, just in case something went wrong. Of course, you could ask your host to roll back a site as well if something went wrong. But if you are looking after 20 or more sites, taking backups and testing will probably take more time than the client is actually paying for.

If not using the auto updating function, how often do you update the plugins?

I use Wordfence to advise when updates are required. In the past I'd go into sites and do the updating, but now with auto updates, I just get notifications when a plugin has been updated.

I take backups of my sites before update.

I use very limited plugins on my sites so I update myself.

I have worked on client sites where the person before me turned off auto updates. When I take over there's a whole bunch of updating to do, one by one in case something breaks...