A big improvement on my previous run in 34 days:

The basic strategy is:

1. build a BIG economy and army
2. attack with Rage of Krolm and Gate
3. defend with Rage of Krolm and Lightning Storm

In my previous run, I tried to amass enough attack power to destroy all the towers in one big assault with no respawning. In this run, I attack a lot sooner from a hero destroying a spire, and simply embrace that some spires will respawn. Only 1 respawns every 4-6 minutes, so as long as I'm destroying them faster than that I'm in good shape.

Overall this is a more dangerous run - more buildings are destroyed, more heroes die. But that's a good sign! It means I spent more resources on attack and less on defense, but still enough that I wouldn't lose.