Noig: Just as a note.
Wordpress seems to need updates regularly, or not?

Almost every package out there these does require upgrading on a semi-regular basis - most of WP updates can be run from the admin part of the site, so no real knowledge is required to do these and only take a few mins to do.

Except when the update goes wrong, or an update breaks the theme. Then you need to also update the theme, and amend CSS. etc. Themes that you buy tend to be quite complex, and they also need updating too, and if they are heavily modified, it can mean quite a bit of additional work after major updates. I just had something break on a theme after the wordpress 3.9 update, and spent the afternoon trying to get it all fixed.

That's why you never edit a theme directly. You create a Child Theme

Yes, but you can still have the same problems with child themes, as they are still using most of the information from the main theme. I always use child themes when making mods to existing themes, but still experience problems from time to time with the main theme and compatibility problems, where you have to make additional tweaks to the child theme.

Sure but exactly the same applies to any CMS that uses themes, even more so to those that do not use child themes.