How long do you hold post for?

[Wellthisunexpected]

We bought a house 8 months ago, the previous owners had a redirect in place for 6 months, in which time I estimated they've changed half their addresses.

For the last 2 months I'm getting 2 or 3 pieces of post a week for them.

I contact them via Facebook to inform them then I've started to leave it under the door mat for them to collect as they'd ask to come when it wasn't convenient.

How much longer do I do it for?

If the situation was reversed, how long would you like them to keep your mail for?
There's your answer.
Putting some letters under a door mat is hardly inconveniencing you, is it?

Add their details to the MPS Mailing Preference Service. It won't stop everything but will reduce a bit of the junk mail. We do this every time a tenant moves out of our rental property.

I'd be doing the same as @Freudianslurp it's not your problem

8 months ago is more than enough time to sort themselves out and change addresses. I'd also write no longer known as this address and put it back in the post box.

Carolynnna I don't expect the owners of our previous house to hold our mail at all. I've changed all our addresses.