Omelets can be served at any meal and be filled with almost any tasty thing. Plus, most take no more than 10 minutes to pull together from start to finish!
All good things take time, and sautéed mushrooms are no exception. You want to give them time to release all their moisture and let it evaporate, so they're browned and juicy, not pale and watery. It's worth making a bigger batch and stashing them in the fridge for future omelets, grain bowls, pizzas, etc.