Hi Martin, I have a Hammer A3-31.
The longest boards I typically joint are about 6 feet long. I do have extension tables however I don't normally use them except on the planer outfeed (at 6 metres/minute feed small pieces were falling on the floor before I caught them).
The longest piece I've jointed has been a bed rail, I did use the extensions, short one on the infeed, long one on the outfeed.................Regards, Rod.