My Infinity Modem lasted a week before it died. First symptom was a drop in the Upload speed, then a day later it died completely with the DSL light permanently flashing.

Give BT (or is it Open Reach) the benefit, they did send an Engineer along the following day to replace the Modem, which is still working after a month. Fingers crossed!

Mine is vertically mounted on the wall and is only just warm to the touch.

BT send the dud units back as they have a years warranty on them.

When I first got my FTTC installed, I had the OR modem and Hub3 sitting on my desk. I did notice the modem getting hot so to avoid any potential problems, I vertically mounted it on the back of the desk. No issues with heating since.

If anything, my Hub 3 is much hotter than the Modem...

Hub sits on my desk with plenty of ventilation.