Our timeline
I think that everyone's timeline has got to be different - different personalities, different marriages, different life stages, finances, job stability, etc.
I am 28 and my husband is 27. We were married a year and a half before we started trying. We're 4 months away from our beautiful baby's arrival!
We enjoyed having our 3 years of dating and year+ of marriage to experience life together. We did quite a bit of traveling, camping, bought a house together, etc. People were always asking us about getting pregnant too (the rest of our friends are couples with children), but that wasn't a reason we decided to actually start trying. We decided it was time because we both really wanted to start having children together and are looking forward to the changes that will come with it.
One thing we didn't discuss as fully as we probably should have before deciding to "go for it!" was finances/my working. We said I would stay home with the kids when we had them, but didn't really discuss HOW that was going to happen. Now, at almost 6 months pregnant, we are trying to figure it out - whether it's financially possible (my husband is also a teacher) and, if not, what the best option will be for our family.
Like I said at the beginning of my post, everyone is different so this may not apply to you, but for myself and my husband, I would not have wanted to trade the time getting to know each other as a married couple and being selfish about our time together to have started a family sooner than we did.