Looking at my current wi-fi I can see one other active router nearby at the moment but that number tends to jump to half a dozen at night, so I think my neighbours probably turn off their routers and computers during the day. I think it's best to just leave things as standard at the start when Infinity is installed and only look at options if problems emerge. I'm hoping the actual router is good.
If you opt out of BT-FON it just disables your hub, you still have access to Bt Wi-fi minutes as part of your Broadband package so you can still use BT Wifi hotspots out and about.
When I took the package you had to opt in to get the hub enabled, now you have to opt out to ge it disabled.
you cannot opt out of BTFON and still have free access to BTWIFI when out and about. It is possible to use a third party router and opt into BTWIFI (BTFON as was) and still have free access to BTWIFI when out and about
imj is absolutely right. This from the BT WiFi T&C for BT BB customers;
Wi-fi access outside of the home is only available if you are opted-in to BT Wi-fi.
At the moment it's all fairly academic for me. The OpenReach engineer failed to turn up for the appointment and they've left me up the creek without a paddle. I was without the phone for 4 hours that was then switched correctly but they just said the switch to Infinity was delayed and they can't tell me when they'll fix another appointment, so right now I have no internet at home. BT never bothered to let me know any of this and I've had to chase it up all myself following the no show.