And so are the ones I knew! Admittedly the much old ones are calm but just pointing out that labs are not automatically a calm staid breed! there ae just so many dogs in rescue and breed specific rescues too that you can really take your time to find number 2 perfect dog. ..
I have got three , 2 collies (mother and daughter ) and a GSD x from the dogs trust . they love to play together and we also have two labs and 3 retreivers that come whenever their owners are out for the day etc . i love to see the dogs interaction with each other .
The labs are very hard work both are young but they go home tired from the playtime they have with mine.
Dogs are a pack animal so I dont think that I would ever have just one dog but then mine are all working type dogs and needs lots of time.
a 'young adult' lab would not really be a calming influence, unless its a non stereotypical lab of course. why do you think you have to get another pup? whats wrong with rescues or buying an older dog?
In your shoes I wouldn't consider a pup, as someone else said you are likely to end up with another dog with issues. I also don't think that they can be left longer just because there are two of them either.
We've always had two dogs and last year lost our last elderly pair within three weeks of each other. I took on an 18 month old lab who had severe separation anxiety and was very stressed, he also lived with another lab in his previous home. It was human time and companionship which has transformed him, the other dog didn't make a difference to him other than stressing his previous owner even more. We still haven't considered getting another yet.
I'd personally go for an older rescue dog if you want another, especially one that doesn't mind being left that may help to relax your dog when left.
It is double the mud/food/barking/moulting and everything such as drying off takes twice as long as when you just have one, I'm quite enjoying having a single dog.
Just an idea ... but what about a cat rather than another dog? We already had a cat when we bought home our rottweiler puppy and they love each other ... OK the dog does get a few smacks across the face when he gets a bit giddy but cat comes and goes throughout the day so gives doggy a bit of company without the additional of another dog