Please read the disclaimer.
Distance sessions are where you improve your ability to walk with good technique for a long time.
If you struggle to walk with good technique – be it bent knees, flat-footedness, chicken-winging, poor breathing pattern or whatever – then the longer sessions give you a chance to CONCENTRATE on improving the relevant aspect of your technique. They are NOT meant as a chance to catch up on the gossip ! Well, for the first ten minutes they can be, but after that time you have started to warm up and you want to spend the session practising your technical points. If you’re just starting and you can’t maintain concentration for ten kilometers, or your muscles aren’t yet strong enough (e.g. shins) or flexible enough (e.g. hamstrings) for you to attempt to walk correctly for the distance, you should do a shorter distance. Take a shorter route back, or break into a jog for the rest of the session. It’s preferable not to just relax into walking with bad technique, because then the technique will become habitual.
How to maintain concentration ? Usually that’s something you must decide for yourself. It’s not easy to concentrate on the same thing, or more than one thing, continuously, for an hour or more. Some people do it by deciding they will concentrate on one thing up to a certain landmark that they can see in front of them, and when they get there, they either give themselves a mental breather up to the next landmark they can see. Or maybe they decide on something else to concentrate on up to the next landmark. Whatever works for you. But as you practise, you will get better at it, and eventually you will develop the strength, flexibility, concentration or the subconscious motor skills to walk well for 10k.
Did you read the disclaimer ?