Any amount of time breastfeeding a child should be applauded, even if it is just one day. Breastfeeding is always best for the baby, but it isn't always best for mum.
The WHO recommend breastfeeding until a child is 2 years old (with complementary food after 6 months) and recognise that there continue to be benefits beyond that time. And no that isn't just in countries where they may not have access to a wide balanced diet because breastmilk isn't just about nutrition.
Anyone breastfeeding their child beyond 2 years almost certainly isn't doing it just because they want to. Some babies self wean before then, but others want to continue to feed for many years. And why would you not give your child something that they wanted, that is good for them (and you), is free and you can provide? (Again I'm not criticising any mums who wean earlier due to a whole range of personal reasons).
The only time it is acceptable to say "are you *still* breastfeeding?" is when the baby is over a few months old, has been feeding for over half an hour and you need the mum for something. Even then you may be given a dirty look.
Definition of Extreme breastfeeding
When the feed has been going on for 2 hours or more. Now that is love (on both sides)