I think it's the right approach. There are many advantages. Upgraded outposts and the main castle. On the first day, it's not necessary to solve super-complex tasks; you can just hang out near the castle, visit some upgrade locations, and that's fine. But on the second day, upgraded scouts will scout more, making it easier to develop the right strategy; it's better to spend a day in place than to go in the wrong direction. Then, you often encounter ranged units that are much easier to defeat with harpies. That's my noob opinion :)
P.S. There's no significant loss of tempo from returning troglodytes to upgrade; most often, on the first day, you can avoid battles and leave them in the castle until level 112.