as far as i can tell the best way to prolong stages for exp/money/drops is to go with spammed maxed turtle, 1 maxed monkey, and then spam heal when u need to, im typing this comment while a stage is auto-farming gold XD (also all the army support skills should be as high as possible for this to work, works best on area 5, stage 19)
o yea, another glitch, not sure if its my perception but guard towers have a capability to shoot MUCH faster than archers/warriers/wizards when they're buffed to attack speeds lower than 10
if you summon 5-10 units in the first 30 seconds of any tier 3 game, the computer seems to automatically send a handful of units without using a global, useful info for people with streamlined kamikaze decks (one can win a game in under a minute this way against elder gornash)