i have only introduced adult chins and i agree that it was really rather hard! mae who's a rescue, we are guessing she's at least 6-7 years old, took six months of intros but they are now very happy together. i'm hoping that this will give her a boost, she's very dependent on me and will not eat while i'm not at home - i normally go see her before work and then straight after i get home, she will not start eating until i go see her which has caused problems in the past when i had to go away for a full day (she got seriously sick).
chinchi was 2 when i introduced him to fluffy and that took about two months.
with both of them, they absolutely adored me before they accepted their partners. afterwards, they liked me still but it was nowhere near the relationship we had beforehand. so i guess they do appreciate having a partner! but not wanting one or a very hard and long introduction is a very real possibility!