What is a healthy relationship timeline?

All depends on the type of relationship you are in and the people involved. Don't look so much for dates or timelines, but rather make a checklist of issues and connections needed for all parties to feel comfortable "moving forward" if that means marriage or whatever you have in mind. Again, each checklist is highly personal. Criteria to review should include but not me limited to: fundamental / spiritual beliefs, visions of your future together, careers, family, lifestyle, etc. The more details you can provide to solidify your perceptions and understand the other's perceptions, the better suited you will both be to determine the direction of the relationship. Remember that relationships are more than just about compatibility. They are also about commitment and will. You may be perfectly compatible with someone, but are you both looking to get the same thing out of the relationship? One key element is that BOTH parties involved need to be "ready" (though the criteria for both may be vastly different) to move forward.