It depends on whether or not one is looking to have a long engagement or a short one. I've known people who were "engaged" without having a wedding date set for years!
Anyone who gets engaged without having any prior major disagreements has yet to see their mate's "authentic self" with regard to how they handle stress or conflict resolution. Committing during the "infatuation phase" is way too early. You want to be certain you can (accept) someone as they (are) and vice versa! Generally speaking people don't change all that much overtime. It takes time to fully get to know someone. At least 18 months or longer of (consistent) dating. People in long distance relationships often confuse "calendar time" with "actual time (together)". Anyone who sees their mate one weekend a month for 12 months has only been with them 24 days and not a year.
If a couple plans to engage and get married within a year after becoming engaged then certain things must take place first in (my) opinion.
Assuming they are "in love" with one another and not getting married for the "wrong reasons" such as an ultimatum was given, unplanned pregnancy, it was someone's "age goal" or all their friends are married...etc
Both people need to have a career path established and get their financial house in order. They should also have frank discussions to see if they envision the same type of lifelong marriage (Number of children, discipline, housework, joint account or separate accounts, college funds for the kids, saving/investment plan for retirement, ideally how many times would they expect to have sex per week, is going to church as a couple/family important?, Boys/Girls night out or weekend getaways acceptable?) Essentially discuss everything that causes divorce.
Contrary to popular belief these things don't "magically" work themselves out. You need to know if you have the (same vision) for the marriage and agree on strategy for getting there. "Opposites attract divorce attorneys!"