my son have use this for the past 4.5 month -lrb- start at age 13 month , since he be in the upper percentile for height -rrb- , and it have work like a charm . very durable - none of the stitching have fray at all , despite weekly washing . Perfect weight with a long-sleeved onesie in the summer -lrb- thermostat around 73 -rrb- or with fuzzy pajamas in the winter -lrb- thermostat around 66 -rrb- . it be roughly 3-4 '' longer than the Halo version that claim to fit the same age range , which have be great for we . overall , we have be very happy with this sleep bag ! Update : he be still use this bag at 26 month , though he be just start to approach the bottom edge of the bag . it be hold up well through many , many washing over the past year , and we still love it !