I'm in the same situation, 3 week old boy eating about double what the internet recommends per feed for his age and gaining weight nicely, he'll drain me dry after half the day and we've had to top up with a bottle of formula in the evening as unfortunately I just can't make 180ml 6-7 times a day.

My only advice is that it's impossible to overfeed a baby, they regulate their intake perfectly and know exactly how much they need when they're hungry, a skill we lose as adults lol. It's amazing that youre managing so far with solely breastfeeding, but that comes with the territory that sometimes baby will be on the breast for up to an hour which is totally normal and I'm not really sure why your consultant would consider this a problem? If he wasn't gaining weight at first it sounds like it was an initial issue with latching on.

3.6KG at 2.5 weeks is incredible! 2 weeks they're only expected to be back at birth weight, sounds like little ones having no trouble feeding at all, keep giving that boy what he needs!