Life changes in a number of ways...
Academics - historically, your sophomore and junior year have more credit hours. It is manageable because you established study habits in your freshman year and ideally learned how to leverage the academic help resources available to you.
Militarily - you will gain more leadership roles as you become a junior and senior.
Quality of life - you gain additional privileges each year. This may not be accurate today, but let's use it as a frame of reference to understand a few of the levers available to you that many do not understand are even something that can be controlled:
Freshman - People yell at you to make you think you can do nothing right, door to room open during the day (every day) until academic call to quarters (after dinner). limited items of memorabilia (they count things like pictures or nick nacks. Limited "passes" to go off base - sponsor passes, day passes, and overnight passes.
Sophomore - People really don't yell at you and you become the instructor for freshman, door closed whenever you want. more items of memorabilia. + a few more passes
Junior - more items of memorabilia, a mini refrigerator. Ability to have a car. Can go out but return by academic call to quarters
Senior - a tv + go out and be back by taps. Virtually unlimited overnight passes to stay out on the weekends.
Considering that your ability and quantity of times to depart campus are managed by class year, and the school can "close the sign out logs" at any time to prevent anyone from leaving (generally for severe weather), that perk is one of the most valuable. Underclassman who participate in clubs or sports that travel generally can travel more than the average cadet because those activities are approved and do not count against your authorized total.