It's exhausting because both partners live with a constant sense of threat. (gottman.com)
Moreover, the overall calm and balance of the composition has the power to counteract any overwhelming sense of threat. (artlyst.com)
Provided you've got your neighbours at least ambivelent to your existence there's very little sense of threat in Stellaris, and thus in almost every game I found my empire stable and safe during the mid-game, capable of pumping out massive fleets. (wolfsgamingblog.com)