My wife will insist that one cup of tea I bring her is amazing, but another one is disgusting. However, they're all from the same box of teabags, made the same

My wife will insist that one cup of tea I bring her is amazing, but another one is disgusting. However, they're all from the same box of teabags, made the same way, and the biggest correlation as far as I can tell is how long she has left it to go cold.