My other limitation is heart rate.  If I pedal too hard, heart rate shoots up to levels I do not like to see it.  I do not have heart problems and I want to keep it that way.  So, I use a heart rate monitor to tell me when to stop, get off the bike, and walk it up the hill.

I never thought about all that when making my choice, 

I am an engineer (retired), so I of course I tried to use a scientific approach.  I tried to pedal up a steep hill near my home several times to see how slow I could go and still feel comfortable that I am stable and not oversteering and overcorrecting.  That was how I came to the 3.5 mph criteria and the cadence of 72.  If I tried a cadence closer to 60, I noticed the slow down and speed up pattern as I pedaled, thus I set my target for hill climbing at a cadence of 72 that felt smoother.

I have pedaled up hills on my Nomad Mk II in first gear with a cadence of 60, thus about 2.9 mph, but those were on good days without wind, minimal traffic on the road so I felt more comfortable being further from the edge, etc.

I had a bike fit years ago when I bought my RST.  Best thing I ever did as it fits me like a  glove.  It's now converted to an E and still going strong.
Kevin Sayles looked me over a few years later and built me a superb Woodrup Chimera.

Thanks Mickeg, interesting ..

Effectively, for me 36x16, the most important gear is the  first, i can climb almost  any hill..

But, my next Surly chainring  have 35 teeths, i got a good price for it,  I don’ t know if i have to keep my sprocket in 16 teeths or maybe 17 ! but i'm afraid to ́lost my first short gear..

For information, 36x16  transmission,  above 33km/h you can no longer pedal, sometimes it’s frustrating

My cadence has varied over time.  For the past few years, it usually is in the range of 66 when I am doing a multi-hour ride.  If I am working to get up a hill in a low gear, I try to raise it up to 72.  But if I have been in the saddle for most of the day already, it might dip down to 60.

I mentioned I use 36T/16T (ratio of 2.25) for touring.  But for riding around near home with an unladen bike, I put a 44T chainring one the bike, add four more chain links for a ratio of 2.75.  For riding near home, I never need a gear higher than 14 with that higher range of gears. 

But for touring, I value that low gear, so I can live with the loss of the higher gear that I would otherwise use on shallow downhills.

When I built up my Nomad, I calculated that if I wanted to use the stock 16T sprocket, pedal at a cadence of 72, and have a speed of 3.5 miles per hour, that I wanted a 36T sprocket.  I find that I can't get below 3 mph without oversteering to try to maintain stability, both directional and vertical.  And a cadence of 72 feels smoother than anything slower.  My point is I did some calculations to figure out that I wanted the 36T, I did not pick it at random.

And the 44T, that range of gears pretty much mirrors my range of gears that I think are ideal for riding near home on my other bikes.

For information, 36x16  transmission,  aboie 33km/h you can no longer pedal, sometimes it’s frustrating

Depends on your pedaling cadence.

I generally pedal relatively fast at about 90 rpm (tours par minute). With a 36x16 combination that translates into 36 km/h, which is way above a sustainable speed for me on the level, unless I have an exceptionally strong tail wind.

If necessary I can increase pedal cadence for very short periods. With a 36x16 combination at 120 rpm in the highest gear that would be 48 km/h. In practice, that kind of speed is not really useful for me, except perhaps when I negotiate medium size roundabouts, where I feel safer if I am doing roughly the same speed as most of the motor vehicules. 

My current highest gearing on any of my bikes is 42x19 on my Rohloff equipped Raven Sport Tour. I use that bike mainly for day rides with little luggage. Top gear with 42x19 is slightly lower than with a 36x16, the maximum speed I managed recently when pedaling (downhill) was 53 km/h at 137 rpm, just to see if I could still do that at age 69. But normally I would just stop pedaling and coast down the hill.