Subplots and Slow-Cooking Romance

On March 29, 2014, maybeawriter wrote, I noticed that I tend to rush through subplots. For example, in one story, I have my two MCs falling in love. They meet the first day, then they're already friends with hints of romance by the end of the second. I know shared life-threatening experiences tend to help people bond quickly, but it seems somehow too fast to me. In the same story, I have a (fundamentally good) character who considers himself a super villain, and I think he abandons his life p...