I have calculated that it takes me 5 months of keeping 1 hero down to max heroes, 6 for defenses and a hefty 1 year more to max lab. I have a mini at TH9, but he's for war purposes and won't upgrade defenses nor walls seriously.
So true, before I rushed to TH9, I was daunted at the 4-5mil costs. But as I slowly got used to it and did lava walls, I grew accustomed to the costs. Now I'm laughing my head off TH10 upgrades which are a measly 5-8mil, which is very small in comparison to what walls cost



