I live in Bend, Oregon, a town of 60,000 and a city radius of about five miles, so 10 miles from one side of town to the other.
I have about a 500' gain and loss around town.
When in good shape, 48X16 seems just about right; I could stay in the saddle on my worst hill.
I had gone down to 48X18 because of a month layoff, and it surprised me to discover I could go just about as fast on the level and uphill with 48X18 as I had with 48X16.
I can't go as fast downhill with the 48X18, but I have so much more control going downhill that I consider it an even trade.
Now that I've ridden 48X18 (70.1") for a week, my legs feel stronger and I might go back to 48X16 (78.8") in a day or two.
With a 48t chainring, the next jump to a 15t cog would put me at 84.1", and I don't know if I could do that.
Maybe if I lost 30 pounds.
(I've got it to lose, too.)