Just read a few internet posts about whether ACF50 has a 2 year shelf life or not, some say it does others say not, so went and looked at my bottle which i bought with the handpump thing, sure enough printed in white is a 'fill date' and a 'best before date' which is exactly 2 years later. I suppose 'best before' is not 'use by' and i have no idea how quickly the effectiveness reduces so i'll carry on using it beyond 22 march 2023. So there it is. dunno if XCP has a use by /best before.