Ahh... upgradeitis. It's a common affliction.
Brutal truth - 5500 miles is nothing to a Shimano shifter of that generation. You mention waiting until it wears out - I have known people with 60,000+ miles on shifters without a problem.
Wanting 11 because ...11? not worth it on it's own.
Wanting smaller gearing? You said you were fine with what you had...The only thing I found by getting lower gearing over the years was that I went slower.
If you are trying to buy new parts and pieces to make a gearing solution to what you already have then yeah it will most likely be less expensive to get a new group.