It sounds like your 2011 Altima SL has been well cared for, which definitely plays in your favor if you’re considering a trade-in. Since you drive a lot, moving to a 2014 or 2015 model with fewer miles could give you peace of mind and reduce the risk of unexpected maintenance down the road.
One thing to keep in mind is the logistics of selling or trading in your current vehicle and making the registration or
title transfer smooth. Ultimately, it comes down to balancing comfort, reliability, and cost. If the 2011 is still running strong and you feel confident about its longevity, continuing to drive it could be fine, but upgrading to a low-mileage model will likely reduce stress on long trips.