I'm 63 and still shoot with the irons only. I do find that using 'no-line' bi-focals is a help...I just tip my head back a little to see the front sight clearly. I was a pilot by profession before retirement and have always had my 'no-line' bi-focals ground with the magnification element a little higher in the lens. This allowed me to see the instrument panel better, and, coincidentally, it's the same distance from my eyes as the front sight on a 6" barreled S&W. That hi grind line takes some getting used to and you may not like it at first. But there may be a better way and far cheaper...
I also use cheap Walmart "cheaters"...1.5o or 1.75 alone, that is not in conjunction with my prescription glasses. I shoot better with these than with the prescription lenses and I don't have to tilt my head back. You'll find fi you try them, that you will only be able to see the front sight in focus, the target remains a blur of varying shades of gray depending on the power. I use only the strength necessary to give me a sharply defined front sight, any more and you lose the target altogether. They're good for target use, but for hunting, I use my regular prescription lenses.
The cheapies also work very well for hi-power across the course competition. At the short yardages, 200 & 300, I use a center of mass (Navy) hold using a wider than average front sight on the AR, to allow me to see the post overlapping the bull. I get good elevation and windage alignment that way. At 600, I use a 'frame' hold. That's holding the front post flat against the easily seen line between the target frame and the berm. Obviously, I have radically adjusted 'come-ups' for that 600 "frame" hold. With the Garand, the M1 Carbine, and 03, I have no choice but to use the standard 6 o'clock hold, since sight width is not possible but they're only shot at the 200 yd line in CMP competition. I use the "cheaters" in the same 1.5 to 1.75 or even 2.0 powers.
As to your question on barrel length, I do like the shorter barrels now in handguns, but shoot the longer, 6" ones equally well. For me, I find the shorter ones are easier to pack around the farm, and may balance better in my hand as I've gotten older.
Those cheap lenses are really the secret...as the old gunny said, it's all about the front sight...YOU MUST FOCUS ENTIRELY ON THE FRONT SIGHT. With those cheaters on, you can't focus on the target no matter how hard you squint...you can only see the front sight clearly. Ah..............if I'd only known 30 yrs ago...I'd have made Distinguished with the Pistol.
Regards, Rodfac (Using my son's computer while away from home...hence the 30cal vs Rodfac discrepancy.)