Newbeginnings - I remember the time it took to feed a new baby but you know, not always does it need to be that long. If you decide that the feed needs to be shorter you can stop it because it is a partnership. So when you are out and about, you could shorten the feed. I wonder if you are waiting for him to stop and let go (which technically is correct) but some babies like to hang on there.
The sign to look for when interrupting a feed is the change to 'flutter sucking'.
When your baby first latches on he will suck quite quickly initially and then when the milk lets down he will take longer sucks in a rhythm and swallow with each one. He will then pause as he waits for more milk to let down and then he will take long sucks and swallows again. He will then go into flutter sucking where it is faster shorter sucks, sometimes dozing for spells in bewteen. Now this type of sucking is good for stimulating later milk production but it is not essential at all feeds.
You can break his latch at this point, pinky into the mouth to break the suction before taking him off, the offer the other breast. Do the same thing again. You will find that he probably will settle after the feed because of the motion of being out and about.
My first son would latch on for hours. I used that to my advantage to avoid making the tea and watching the spaos on the telly
When I had something I needed to do, I dicated the time of the feed.
When I had DD (4th baby) she was on and off like a yoyo when I went to playgroup, nursery, school etc with the other 3.
HTH.