Yes, please leave it alone. Nothing prompts me to leave a service I've been with for a long time than a UX "refresh" after I had years of experience and setting everything the way I liked it.
I think this is such an interesting issue. On one hand as a system developer, you want to keep existing customers happy with what they are used to. On the other- you want to grow and acquire new ones which requires upgrades to existing processes till you reach a limit - you need a new ui/ux. And what do you do? Maintain N versions?
The problem, as usual, stems from businesses prioritizing growth above all things (including the existing customers). There's absolutely nothing wrong with having a stable business that turns a respectable profit, but modern day American business culture is allergic to the idea.
