Being a developer is a bit like learning non-programming languages. More immersion and time spent with a new language means more competency. Make certain developers are following good principles. When a comfort zone is established, take them out of it periodically. Give the development team room within the day-to-day or week-to-week to broaden their knowledgebase and feel challenged. Let them code, experiment, learn, make mistakes, and ultimately flourish on their own, especially if there really isn’t room for new technologies or taking any risks while they’re on the clock.