Smartphones and tablets don't come with an expiration date - but perhaps they should. Most people's smartphones get updates to the operating system only when the carrier gets around to it. Eventually the carrier and the original manufacturer consider them out-of-date and stop the updates.
But wifi hotspots, desktop computers and even commercial networks don't block these old devices from connecting. An old phone or tablet with security issues can still have lots of your files, passwords, pictures and data on it, and it's far easier to break into than a newer device.
What to do: