Even 2 years before I applied for my wife, the fastest applications from Vietnam would take about 6 months according to what forum users were posting. These were very strong applications, even stronger than mine, such as a couple being married for 5+ years, having a kid already, etc. I wouldn't say my relationship profile was near the very top in terms of strength, but my wife and I spent a great deal of time preparing the application, sent in 400+ pics, thousands of pages of chats, photocopies of all envelopes addressed to each other with letters and gifts, photos of each of us spending time with my parents as well as her parents, receipts of honeymoon and the trips we had, etc. I think this helped us greatly to speed up the processing time, as my wife has no security, criminal, or medical issues. She's never attempted to enter Canada via a study permit/visitor visa, etc. Never overstayed in other countries. I brought my entire family from Canada to attend the wedding in Vietnam. Honestly, I have to say it was extremely stressful putting together that PR application. I don't know how the Singapore VO picks and chooses files, but I truly believe that a strong PR application that's straightforward helps them to make their decision a lot quicker to approve the visa.
Another thing to note was when my wife and I started a relationship, that was when I started to look at the sponsorship process. The reason I did this was I'm at a point in my life where I really hoped to find a lifetime partner, and I didn't want to date someone that I didn't see having some sort of future with, and I knew if my relationship with my wife was successful that I would like to marry her. Although I wasn't knowledgable about sponsorship at the time we were dating, I knew that it wasn't as simple as just signing a few forms. After reading about what red flags Singapore VO was looking for, what relationship proofs are needed, etc, I came in extremely prepared when it was time to apply for sponsorship. Even before then, I made sure I did everything that was "expected", such as having a traditional wedding, taking pics with both sets of parents, not rushing to marriage, etc.
I do notice that quite a lot of people don't know what to expect for sponsorship after marriage, and they only begin to realize the "red flags" become a problem after the fact, and can't really change it, because you can't go back to change the past. Like for example, maybe if a couple realized early on that a short courtship before marriage was a red flag, that they'd maybe would date for a while longer before marriage to strengthen their application.