Its under 6 months old and one would expect a few years life, so yes should be replacing it under standard guarantee. Though you should only expect a replacement HomeHub and not the newer Smart Hub
Changing the contract and remaining on Infinity 2 is a pure paper exercise and nothing to do with the cabinet and port capacity.
There are loads of issues with the Wi-Fi on the Smart Hub, there is a massive post on here about it and also on the BT site and others.
We are also suffering with ours where all our wireless devices will be stuck in a "connecting", "saved" and back to "connecting" loop, and I have to disable the Wi-Fi and then re-enable it to fix it until it fails again, normally every 4 to 7 days this will happen.
I will also be taking this up with my case handler at BT when they phone on Tuesday.
- Infinity 4 - 310Mbps (down), 31Mbps (up)