I have been using a sleeping bag since the first night the baby was home, as she was born in winter. Even in summer, due to the air conditioning, we had a light sleeveless sleeping bag, like a little sheet, and with a short-sleeved onesie, she was comfortable. I never covered her with a blanket or duvet except for daytime naps. So this winter, which was nearing the end of the season, after a lot of searching, we decided to get this one. It is really cost-effective because it can be used for two consecutive winters. The sizes are made in such a way that you don't 'throw away' your money in a few months. I personally got it for €80 and I don't regret it at all. It is one of the best purchases. The bottom part converts from a bag to 'pants' and now that the child is walking, I take her little feet out until she falls asleep, and this way she is completely independent (inside her astronaut suit).
It has detachable sleeves and you decide what to put underneath. Personally, with the heating a little below 22 °C at home, I dress her in a long-sleeved onesie. I don't want her to get cold, but I also don't want her to overheat. And this way, she has very good sleeps. It's worth it more than anything!!!

Perfect quality! Wonderful design, suitable for multiple seasons since the sleeves are removable (it also helps that we live abroad, so it only lasts a little in the summer). It is also important that it is cotton and breathable! We bought a second one and we wear them alternately, very satisfied.