I always try to add a second country in my trip, but I'm afraid it'll be too much.Lived in Scotland for 5 years and it's awesome. But there's so much to see and do in Ireland I personally would focus on that one place unless there's something in particular in Scotland that's important to you.
This is us too. We rent an apartment in a village we like and plant with some day trips.Yeah I've been on those trips to Europe in my 20s where I just tried to pack as many countries in as possible and I think I'm too old for that shit now. I'd rather pick one place and explore a lot more/make it more leisurely but if I have a whole extra week I was considering going to Edinburgh too.