15 minutes is just enough for me to get dd to school or back. I have to prepare a freezer full of kongs weekly and make sure he also has a green-feeder of kibble and a chew as well to keep him busy. He starts to yell the minute he stops eating and desperately needs to learn to settle himself without food, but no luck with that so far. Daft thing is, when I'm ill in bed upstairs I don't hear a peep from him all day and he often spends all day in a different room to me, so he doesn't actually need me he just wants me to be there just in case. 
At the end of the summer term, while my neighbours were on holiday, I trialled going upstairs and lying on the bed for half an hour, then sneaking out the front door and he was fine. I managed to go out for almost two hours and he didn't notice I'd gone!
Ironically, my neighbours complained when our older dog started howling after our old dog, who he was very close to, died. (My neighbours are actually lovely, but child, pet-less, retired and home all day every day.) I did a separation anxiety programme with him, which worked to the point of him being able to be left for about an hour and a half, but then, through lots of research discovered he actually has isolation distress, not separation anxiety (basically he is fine as long as someone, human or animal, is with him) so we were advised to get another dog.
So, we took on a rescue pup that had, unfortunately, had a truly dreadful start and as a result is highly anxious and over-attached. So now the older dog is fine when we go out and just sleeps, but the younger one screams like a banshee.
His is definitely separation anxiety and it's mainly focussed on me, but he's gradually got a bit better at staying with dh and/or my older two boys - although he still whinges the whole time, but thankfully not the full on screaming that bothers the neighbours.
I've done a lot of work with him and he will improve to be able to be left for up to an hour, but then regresses every school holiday or if I am ill, which unfortunately is fairly regularly. The good news is that it's fairly quick to build up the time again each time now that he's done it before.
I find it difficult to do a proper SA desensitisation programme with him, because he picks up leaving signals so easily and I have three dcs to get to three different schools every day, plus a ds with ASD who needs routine.
I've had him for two years now and my life has been completely constricted because of his SA. I'm currently learning to drive, so I can at least pop to the shops or a local cafe and leave him in the car with our other dog for a short while to get me out of the house, other than for dog walks, occasionally. For some reason he's happy to settle in the car, as long as our other dog is with him and I have on occasion had to resort to putting him in there on the drive for school assemblies like Star of the Week etc, where you get short notice and I haven't been able to arrange for someone to sit with him. We're lucky to have a longstanding good relationship with a brilliant boarding kennels as well, so were able to get him used to staying there with our other dog and he's happy there now, so I can at least get the odd weekend away or put them in there for a day/night if we want to do a family day out.
I've been through cycles of being so upset and frustrated at the situation, just as my last dc went into school full time I ended up with a dog that stops me having any freedom, but I've come full circle now. It is what it is, I know I've always had a tendency to end up with the dogs that would have just kept bouncing back into rescue and I won't give up on them, so I guess he's here for a reason.
My biggest worry is what will happen when our older lad dies. He's 10 this year, so there's an 8 year age gap and it will happen eventually. I'd really rather not take on another dog for him to teach to howl/scream, but I know he'd never cope as an only dog either. Suppose we'll have to cross that bridge when we come to it.