Getting engaged, or married for that matter, by a certain age or number of years you've been in your relatiponship puts nothing put pressure on the both of you. Those numbers are simply arbitrary and should never be used as a time to get engaged.
Instead, you must first identify what it looks like to live your ideal marriage.
Some younger couples who have yet to figure out what their school or career path even looks like might experience more challenges along the way if they get married early, versus a couple who has it 'figured out'.
If you are in a serious relationship, you have the luxury of deciding the level of struggles you both will experience. It's like a choose your own adventure.
Married early=more struggles, married later=less struggles.
We chose the road of getting married and going to college with 2 young kids. That was HARD! And if we could do it all over again and keep our family together, you betcha we would have waited to get married.