Agreed. The problem happens with convincing your clients to pay you to do so.
I have a client that I've been telling for 2+ years to upgrade from Rails 4.2.3 (and Ember 2.8), but they only now funded it. So I'm having to do 3+ years of upgrades and it's a huge headache.
And at the end of it, if I've done my job correctly, the app will look identical.
Rails at least has upgrade guides and a script that allows you to upgrade the app. It helps to go from one point relase to the next. I also find the Railsdiff web app helpful in comparing changes from one release to another. It's definitely not perfect or pain free though. I also hope you have a good test suite :). Good luck.
I have a client that I've been telling for 2+ years to upgrade from Rails 4.2.3 (and Ember 2.8), but they only now funded it. So I'm having to do 3+ years of upgrades and it's a huge headache.
And at the end of it, if I've done my job correctly, the app will look identical.