You could even drop the easy 12 miler and see little drop off in time.
A few years ago when I was 46-47 I was running 2 times a week averaging 15 miles per run. I will say that it gets very tough running 2 long hard runs every week. It would take me all of the 3 or 4 days to recover.
I would usually race a half to 30k every week and do a 12 to 15 miler in the middle of the week. If I didn't race, I would run pretty hard one of the runs. I got in great shape running 30k at 6:45 pace. Thought I could get around 3 hours for the marathon but didn't run one.
I did the elliptical on the off days.