Software: weekly
Plugins and platform software release fixes constantly, and security patches are reverse-engineered by attackers within days of release. A weekly update routine, with a backup first and a quick check of the site afterwards, keeps you ahead. Big version jumps (a new major WordPress or WooCommerce release) are worth testing on a staging site before applying live. If nobody on your side will do this reliably, that is what a maintenance plan is for.
Content: quarterly review, add when useful
- Check every quarter: prices, hours, services you no longer offer or newly offer, team photos and names, the copyright year, the phone number, forms still delivering.
- Add when you have something: a new service page, a completed project, an answer to a question customers keep asking, a change in regulation that affects them. A page a month is plenty; see does my website need a blog.
- Refresh evergreen pages yearly. Update the figures, replace the dated examples, and set the 'updated' date honestly. Search engines and readers both prefer a maintained page over a new thin one.
Design: when it stops doing its job
Not on a schedule. Redesign when the site looks untrustworthy next to competitors, when it is slow or awkward on phones and the fixes would amount to a rebuild, when the business has changed what it does, or when the platform has become a dead end. Three to five years is typical, because that is how long it takes for design conventions and devices to move on. How much a redesign costs explains what the project involves.