Got to love a good sense of humour 
Hi Mark and welcome, welcome, welcome 
So you’ve finally made it to the forum too. Took me about 2 years too 
It is the concentration isn’t it, I understand that perfectly. I very quickly cottoned on to that one, so my signal to family and friends was “brain shutting down now”. So if I was on the phone to anyone I could just say that and they’d immediately hang up without offence…even worked with face to face conversation. My daughter and I just refer to it as "my f**ky brain though to everyone else “it’s just the stroke effect”. So I’m not expecting you to read all this in one sitting 
Doing anything was in fits and starts, a few minutes here, a few minutes there but it has built itself back up to being able to actual complete the tasks I start now
And conversation has improved a lot for me over the 2 years too, to the point it isn’t much trouble, don’t need my signal, but still can be draining from time to time. I think that is more to do my aphasia from the stroke. I’ve always loved reading so forced myself to persist with it and now, the only quirk I have remaining with reading is my tendency to skim over or skip the last line of every paragraph. And if I try to make myself read it, it’s a battle of wills with my brain…it just wants to cut off that line every time 
I’m fortunate that my daughter is studying psychology at university and seems understands perfectly where I’m coming from. So she was better able to help the to help my hubby and son understand too.
Maybe getting your wife on here to read just this post will help her enormously to better understand what is basically the new version of you.
The brain has so much to do after a stroke and it can only do so much at a time without feeling overloaded. Too much information still coming in whilst also fighting to repair damage and retraining the various functions that have disrupted or lost. And it all takes time and is exhausting, that’s why we are so tired all the time.