I thought it might be worthwhile posting my long term experience with the overall battery performance of the two pairs of Anker Soundbuds Slim+ earphones which I have been using for a year.
Both my pairs of Soundbuds Slim+ achieve 5.5-6 hours of listening time with volume set at approximately 50%. I’ve never attained the advertised 7hrs - I assume this might be possible if one was to use a lower volume of perhaps 35%. Full recharge time is about 90 mins.
I fly London-Dubai a lot and use the Soundbuds Slim+ as my main in-flight earphone since I’ve never been comfortable with over- or on-ear headphones. Flight time is typically 7 hours and I’ve always had to swap over to the second pair after 5.5-6hrs due to the battery running out. Hence my need for two pairs.
Passive noise isolation is very good, though admittedly not to the level of any decent active noice cancellation over-ear headphone, including the one provided in-flight by Emirates. The wired connection between the Slim+ earbuds is an advantage over “truly wireless earbuds” when flying since I don’t need to worry about them inadvertently falling out of my ears into the seat crevices when I sleep! The earpieces are comfortable for my ears to wear for 7hrs straight without soreness or fatigue. Your mileage might vary!
I’m usually a month between flights and recharge the Slim+ earphones fully on arriving home. I top them up the day before flying and even after 4-6 weeks turned off sitting in my travel bag, the charge level remains at 90-100%. That’s decent low bleed battery drain!