So there's this achievement 'The Beloved Farmer' which requires you to reach a 10-heart friend level with 8 people. I'm not sure if you're still required to give bouquets to people when you're at a 8 heart level with another person to reach 10 hearts (since that's how you reach 10 hearts with a prospect romance/future spouse).
Would it still be possible to reach 10 hearts with others even if you're married?