Not my experience at all so far. I’ve had the base model MacBook Air for 15 days. I charged it to 100% the day I received it and kept it plugged until setup was done. I used every night for watching video, surfing, downloading and installing software, etc. One full week later it was still at about 15%, but I was forced to plug it in because I wanted to install 11.1.
Now that I’m done getting it all set up and have moved on to just using it (this week mostly for Affinity Publisher and some other odds and ends) the battery drain doesn’t seem to have changed at all. I’m plugging it only once every 7 days or so, even with heavier-than-average use.