How I plan to prepare for a 2.49 marathon in Chicago in Oct 2022

I ran a 3h 54 min in New York in 2010 (30 years of age).

A couple of months ago, in Oct 2021, at 41 years of age, I ran a 2h57 min marathon in Long Beach California (my journey to sub-3 is in this story).

I hope to run under 2 hours 50 min in Chicago for which I was approved and am registered.

I’m very pleased with my sub-3-hour marathon but getting under 2 hours 50 min (6.27 per mile pace) is not a trivial challenge. My pace for my Long Beach Marathon was 6.45 min/mile (6.43 according to my Garmin, as it shows the total distance of 26.37 miles). My fastest long run is a half-marathon at 6.32 min/mile (total time 1h25m.37s). It was a Sunday run in Irvine, CA, in May 2021 — not a race; I felt good on that day and made my long run exactly a half-marathon. It was an exceptional run on that day, not easy to repeat. I have less than a handful of long runs at below 6.40 min/mile.

Currently, I do my tempo runs — 7 miles at 6.10–6.15 min/min. But I have doubts about these being true tempo runs — it feels like I’m running too hard to get that pace.

My current pace range for my Sunday long runs (15–16 miles) is 6.42- 6.59. I have doubts about my long runs too — again I might be doing them too fast, close to how I’d race in a marathon. You’re not supposed to run your long runs at your race pace.

I could probably get a sub 6 min pace on a 10k race (so under 37 min 30 sec).