I ran 1:27 last year at 45 years old off about 40mpw, slightly less on average. If you are going to do lower mileage, you need to do harder efforts. I did a 10 mile training run at 6:55 pace about 2 weeks prior to the race.
I didn’t do any track or intervals, just some tempo and progression runs. The fastest mile I ran was a 5:48 at the end of a training run (with wind at my back). About 10-15% of my miles are sub 7. 30% are low 7s, and the rest are high 7s low 8s.
It took about 2 years after a 5 year break to get there. Ran 1:35 about 6 months in.
I’m now up to about 50mpw and pretty sure I could break 1:25 at the moment. So, yes extra mileage will help. But if you are at least 10 years younger than me and not overweight, then 40mpw should be plenty. It got me to 1:19 when I was in my early 30s.