It’s not good practice to simply delete old web pages if people might still be looking for them.
As an example, if our Mk.I blue widget is replaced by a Mk.II version, it would be daft to remove the original page from the website; existing users might be looking for information on the product for many years, not to mention people who didn’t know there was a Mk.II.
However, what about stuff which nobody would be looking for any longer – a blog post about our stand at WidgetEx’21, for example? I think it depends on whether there might be something related to the topic in the future. If we’re likely to be at WidgetEx’23, keeping something relevant on the site might not be a bad idea.
Perhaps rewrite the ‘Blue Widget Company to exhibit at WidgetEx’21’ article as just ‘Blue Widget Company at WidgetEx’ and review the exhibition?
The same principle can be applied to withdrawn products – if we’re selling alternative or updated replacements, then the old product page can be transformed into a guide to remaining resources about the product and – crucially – links to the new products. If it’s a market from which we’ve withdrawn, pages can be deleted.