Mila Kunis says she doesn't want her marriage to Ashton Kutcher to stop evolving.Matt Winkelmeyer/GA/The Hollywood Reporter via Getty ImagesMila Kunis says knowing Ashton Kutcher since her teens has made their marriage easier.That's because they both already knew "the good, the bad, the ugly" about each other, she said.Moreover, their long history has given them confidence that they can continue evolving together.Mila Kunis says years of growing…