As for me... well I am up to 22k LSR but my legs are pretty tired at the end of that. I am alternating the LSR with a reasonably challenging (for me) hills session, and for the rest a mix-up of 2 minute sprint sessions and easy, depending where I am and what the surface is - trying to avoid too much hard roads work. I get to the gym 2/3 times a week and there I do ergo sessions or core / weights, so my cardio is good, it's all about stamina now.
I'm hoping to do the Marlow Half - 1 November - and will probably look for a 10k / other half before that as well. Nothing booked yet.