Fresh fresh, new new what ya gona do if Google kills you.
For years Google told us to be brave, be nice and behave and build a large website with many links to it to become authoritative in the field we were operating in.
Write about your product, business with the intention to inform your visitors / customers.
Now, with the hunt for being the fresh prince of search engine land, old sites are being ranked lower and lower to favour the newbies.
New websites on generic domains with little or no content at all are favoured just to satisfy the hunger for new fresh pages.
So, if you have a site on which you have almost literally wrote about every single aspect on your product you could think of and these infos aren't likely going to change, the only thing you can do to prevent a drop is to write new content.
Rewrite the old stuff, even if it still is as up to date as it was when you wrote it years ago.