If you are considering lateraling to another firm, there is no more pivotal time in your legal career than the fifth year of practice. Your fifth year is when you should start thinking about finding a new job if you're not happy with your current one. Do not stop. Do not pass go. Get your resume ready, think about what you want out of your next job, and get in a mindset to move. If you are truly happy where you are and it's going to get you where you want to go (in-house, to partnership), count yourself lucky and then sit pretty.