My training sessions per dog tend to be super short. Very rarely would I spend ten minutes on a skill at one time. I mean, it depends on the type of thing but for "small" skills, meaning ones which are very localised, or very precise - so pretty much anything indoors - I *try* to aim for one minute sessions, with as many reps as possible in that one minute to keep a very high rate of reinforcement. In actuality, they normally spill to two of three minutes, but when I am thinking about it, one minute is my optimum. Obviously once we start chaining behaviours together, the time has to expand. And with multiple dogs, I rotate the dogs so I will do several sets of that (hopefully) one minute in one session, with them getting a break - and reinforcing their ability to wait their turn - in between. So I might train for, say, 15 minutes, but the dogs will get a minute session, followed by two minutes of stationing, repeated three times.
What I train depends entirely. If I'm training a certain subject, there are normally enough exercises that can be used for that subject that I don't bore myself (because if I am bored, the dog will be bored). So, let's take a station behaviour, for example. In one session, I might just be loading the station, paying 5-10 treats for being on it, throwing one off, repeat until the dog is pushing to get back on the bed. Another session, I might be "trying" to lure them off the bed whilst they work to stay on. In another session, I will work on steadiness to food/toys dropping around them. In another, I'll be working on energetic releases..... so a single subject, but loads of different exercises around that subject.
With a baby puppy, there is so much stuff that I think is important to cover, and most of that for me is around life skills. Husbandry is a massive thing for me, so training for eye drops, nail trims, general handling, teeth brushing.... I think all of those are far more important than a puppy who will sit on cue, and I train them every single day. Chin rests - so useful and a massive part of vet visits and cooperative care.
Then the incidentals: I hate it when dogs get OTT when they know they're going on a walk. We had a few dogs like that when I was growing up and it was too stressful. So learning that that is a calm activity. Loose leash walking, recall, walking at (or near) a heel position off leash. Dismissing other dogs and people. Checking in. Waiting to go through doorways. Car skills for getting in and waiting to be got/called out. Sitting quietly while you stop and talk to someone (or have a coffee etc).
There are just so many things that you can choose to train, based on your needs, your dog(s), your personal preferences, that it can be overwhelming to decide what is most important. I am totally blasé about the things most people obsess about. Squidge didn't learn to sit on cue for aaaaages, because I just didn't (and don't) see the relevance in teaching it. When I did get around to it, it took a couple of minutes because by then, she knew how to learn. Why people insist on it being the first thing they teach, I have no idea. But I am not them, and they are not me.
In essence, it doesn't matter what I do, or what I say. You have to choose the things that make most sense for you and your dogs.