Content — depends on the type of site. A blog or news section benefits from regular updates (e.g. every few weeks); a static business card — less often. Fresh, useful content helps with SEO and shows the site is “alive”.
System (WordPress, PrestaShop, plugins) — security and maintenance updates are best applied regularly (e.g. monthly or when released). Old versions can have bugs and security issues. Back up before major updates.
There’s no single rule — the main thing is that the site isn’t left untouched for years, in both content and software. Technical support can include monthly updates and small content changes.
