And this is why my post got too long. I used a book of heroes which meant I need to farm a huge amount to make it worth it. Let me explain.
Book of heroes is only as good as how fast you can farm. It is generally not useful for below lvl40 because you aren’t cutting the maximum amount of days. However, do use a book of heroes if you have free ones coming up from clan games or events.
For AQ lvl40+, her cost exceeds your DE storage so you can only upgrade her once and need to farm more to upgrade her again. A book of heroes normally costs 500 gems which is 3 days. If it takes you 4 days to farm the DE for AQ, it means you only saved 3 days of AQ upgrade time which is the same cost of buying the book in the first place. This means that the book of heroes is ultimately useless because it did not reduce any hero upgrade time at all.
Thus, BoH is only as worthwhile as how fast you can farm. If you can farm the DE in 1 day, that means you are saving an additional 3 days of AQ upgrade time. If it takes you 6 days to farm the DE, then BoH is essentially worthless because it only reduced one day of time, with a cost of 500 gems.
Since I’m using a BoH, I will need to farm hard today, 160k DE in a day
AQ lvl42 and awake, time to farm. Using that hero builder for a gold mine and I have 27 hours to farm 160k DE, let’s see if I can do it
Both heroes awake, so I can use full armies every raid. I also only hit bases with a decent amount of DE when I’m farming DE. Normally, I don’t really care about DE because it will overflow in 2-3 days but I don’t have 2-3 days now.
Getting lots of DE, and this is 10 hours of farming:
About 110k DE in 10 hours, pretty reasonable but I didn’t actually farm 100% of the time. I will need to farm another 50k in 12 hours which will be easy. But this picture was taken at bedtime so I need to rest now