When the foundation is wrong.
THE SIGNS
You cannot achieve what you need without extensive workarounds The theme is no longer maintained It is slow and cannot be optimised further It does not work properly on phones Support is unavailable
THE WORKAROUND SIGNAL
Writing extensive CSS to fight the theme means the theme is wrong for the site.
THE MAINTENANCE SIGNAL
No update in over a year is a warning.
No update in two years is a security problem.
THE SPEED SIGNAL
If the theme demo is slow, your site cannot be fast.
WHEN NOT TO CHANGE
Because you are bored with the design Because a new theme looks better in a demo
Changing theme is disruptive. Have a real reason.
WHAT TO DO INSTEAD FOR A REFRESH
Colour, typography and imagery changes achieve a great deal.
WHEN A CHANGE IS DUE
Plan it properly, on staging, with time to test.
Not on a Friday.