Yes, people change:
1) Some change to make their life better.
2) Some fall out of love, have an affair and divorce along the way or continue to sleep in the miserable bed they'd made and continues to cheat.
3) Majority will change to be a better husband/wife and greater lover when s/he finds the one the second time around.
Let me tell you, when you have a good spouse and doesn't cheat on you.....work hard to keep the flames alive. There's no better love than his/her love.