This thread has several uses, and it should be pointed out, given the refresh, is that this thread can be helpful for people with separate tickets, in other words booking a third country itinerary. For example booking HEL-LHR-PHX rather than LHR-PHX with a separate LHR-HEL ticket to link into the longhaul. This thread indicates that it isn't too risky to do this and to some extent what we are talking here are those locations where booking a true back to back wouldn't be too risky with 2 tickets: The return flight can't depart for 35 to 45 minutes minutes after the outbound service. Essentially the question is whether that 35 minutes is enough time for you to arrive and get around to the departure gate.

Clearly doing it on one ticket also gives you protection to a degree but personally I think it is easy to overstress the advantage of a single ticket on a back to back, if you didn't get to the return service's gate 20 minutes before advertised departure time then that protection is potentially toast anyway. And if you're in a smaller airport with 3 services a week, with Iberia doing the handling, and it's 23:00 hrs, then good luck with extracting that protection! That's my personal view.

And while I'm here, this thread is rather less useful for those who want to take non B2B services, perhaps on the basis that an extra 3 hours gives more comfort to the connection - that is potentially a false sense of security since if the outbound is delayed, the inbound - on a different aircraft and crew - could still run on time. Clearly if you have checked baggage a true B2B becomes very difficult, I have only found one or two places where this is possible (e.g. some LGW-CGN services, some LCY services to places like Dublin and Milan). In which case, it may be better to make a virtue of a visit to the city concerned, and go the night before.