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MerlKori, the growth rate of all level 6 units is about 1 per day when the shop is opened by the player. In a shop that hasn't been visited yet, the rate is lower. Paladins were unlocked earlier, so there are more of them than Ents. The growth rate is small to prevent the possibility of hiring an uber army, forcing players to rely on additional boosters.
And what are the boots for? There's no need to rush here.