"Run in" may be used in a variety of contexts, from referring to a car's break-in period to a new employee getting familiarized with their job. However, if you find yourself using the phrase too often, it may become repetitive and dull. That's why it's essential to have a good pool of synonyms to choose from. Some alternatives to "run in" include "ease into", "acclimate to", "get accustomed to", "settle in", "adapt to", and "become familiar with". Use them to keep your writing fresh and engaging, or to spice up your vocabulary in everyday conversations.