Old eyes or not, you can't hit what you can't see. For target shooting there is every reason to get the most magnification you can.
I agree, even with a larger target you can't tell exactly where the crosshairs are sitting if you can't see the target clearly.
The unmentioned advantage to higher mag scopes (clear ones in particular) is that you don't need a spotting scope to see your bullet holes. At 18X, I can clearly see .22 holes at 100 yards, although on a black background it's not as easy.
There's a marked difference between what I call "cheap magnification" and "clear magnification". I can buy a 6-18 cheapy scope for under $200, but I often can't see sh#t through it at higher mag settings, which is the whole idea to begin with.
After a few days of eyestrain and frustration, the extra $ to get something top quality seems like a drop in the bucket. Plus, every scope that top shelf manufacturer makes is a consistent product, you're not "hoping to get a good one".
The rule of thumb "expect to pay what you paid for your rifle" isn't accurate (pardon the pun) IMO when it comes to target scopes. I expect to budget 1.5 to 2 times the rifle cost. I'm talking CZ here, not Anschutz.
I certainly don't regret dropping what I did on a 6-18 Leupold for my Varmint, if anything I should have gone higher for more power, but it's fine for what I do with it.
The 3-9 is probably going to be for sale soon, it doesn't get used much. Great scope just the same though, sharp and clear with the flexibility AO provides for close range shooting.