Hi my wife and I are retired and came back to the UK from living in South Africa for the past 30 years, just wanted to get back. We didn't have any narrowboating experience, but just wanted to try it. If you want to do it, then JUST DO IT. I agree that water, electricity and toilet are things that start to absorb your life, but despite that we did it and it's been ok.
So if you want to do it, then do it, as long as you are reasonably fit and agile and also have a smaterring of common sense and some mechanical ability then you'll manage.