My pup is 4.5 months and on 3 meals per day, he doesn't tend to eat all of it though which is why I am wondering is it his time to go down to two meals, but then i wonder that because he is a large breed, should we keep it to 3 for longer...

It is usually 6 months old and they stay on that for life or when they reach 12 months old I revert everyone back to free feeding which I stop when I have pups on a different diet.

Cutting back to 2 meals doesn't mean they eat any less in the day just more at each sitting.

True but I wouldn't like to think he was going hungry between say 10am and 5pm if there would be typically a meal at lunchtime.. i'll hold off until 6 months, not long to go - hard to believe!! :)Thanks.

Usually you can tell when to do it - the pup either starts to get a bit plump on 3 meals, or starts to go off his/her food a bit (not hungry).