TH upgrade time = 12 days
Lab upgrade time = 6 days
Arch 6 = 10 days
Poison 3 = 6 days
Start arch now and start TH at the same time. 2 days before TH finishes, start poison and save up enough elixir to upgrade lab. Every second you spend now in TH9 is a second away from a maxed TH10 or maxed TH11. Lab is the only bottleneck of the game, everything else can be done or caught up in reasonable time.
My own TH10 had half legos, TH5/6 defenses and 20/0 royals (kept AQ under the knife) when I moved to TH10. Now as a 2 week old TH10, I'm doing just fine. Hero levels are a non-factor in farming, and if they are, you're farming wrong.
Read:
https://clashguideswithdusk.wordpress.com/th10-journey/