What age to retire the sippy cup?

My daughter is 18 months old and is using a straw sippy cup and does also use the gerber hard spout ones. When should I begin to wean her from them? How do I do it, I mean do I just go to a regular cup or is there a certain sippy cup that is better for older toddlers? I have seen some with a small hole that looks more like a regular cup where the juice just comes out into the top and then they sip (doesnt make to much sense its hard to explain). First time mom and any advice would help!