After mature consideration is a phrase that suggests a thorough and thoughtful examination of something. There are many synonyms that can be used to convey the same idea, including after careful thought, after due deliberation, after weighing the pros and cons, after thoughtful reflection, and after serious contemplation. Each of these phrases conveys a sense that careful consideration has been given to a matter, and that a decision has been reached only after careful consideration of all relevant factors. Ultimately, the choice of synonym will depend on the context in which it is being used, as well as the intended tone and nuance of the message being conveyed.