We used Grobags on DD1 in her toddler bed (cot converted) until she was 26.5 months. She made the call to use the sheets and doona on her 'big girl bed' (king single) so that's when we stopped using bags. We would have continued using them had she wanted to or needed to but she's taken to normal bedding well and can pull the bedding up (or down) depending on the temperature.