American technology companies are looking ahead to the future of office work after the coronavirus crisis. Some are considering whether to permit employees to keep working from home, as most have been required to do for the past few months. Companies including Facebook, Microsoft, Apple and Twitter were among the first to send their employees home as the coronavirus spread to the United States. Now, some of their employees might never go back. The companies are studying ways to give their highly valued employees what they want. They are seeking to use their own technology to make remote work easier. They are also looking to hire new workers who live outside of big cities. Silicon Valley has long operated by establishing large work centers in major cities to appeal to high-quality workers. But the lasting effects of the pandemic could change that.