Almost everybody uses too much, in the wrong place, for the wrong length of time. Fixing that is free and makes the bottle last twice as long.
When somebody tells us a conditioner did nothing, the first question is how they used it, and about eight times out of ten the answer explains the result.
Quantity first. For hair to the shoulders, a conditioner wants roughly the amount that sits in the hollow of your palm without spreading, which is far less than most people put on. More than that does not condition more. It sits on the surface, weighs the hair down, and gets rinsed away, which is the expensive part.
Placement second, and this is the big one. Conditioner goes on the lengths and the ends. Not the scalp. The last few inches of your hair are the oldest and the most damaged, and the roots are the newest and the least damaged, so putting the conditioner where it is least needed and skipping where it is most needed is exactly backwards. Roots that feel greasy on day two are very often a conditioner problem rather than a shampoo problem.
Third, the water. Squeeze the hair out before you apply anything. Conditioner going onto hair that is dripping is conditioner being diluted to the point of doing very little, and it is why so many people feel they need to use more.
Fourth, time. One minute does most of the work of five for a daily conditioner. A mask is different and genuinely wants its five or ten minutes, but leaving a mask on for an hour does not do more, whatever the internet says, because the strand has taken up what it can take up long before that.
And fifth, rinse properly, in water cooler than feels comfortable. Product left in the hair is the most common cause of hair that looks dull two days after washing.
Do all five and a five hundred millilitre bottle that was lasting you six weeks will last you three months. We are aware of what we are saying. We would still rather you knew it.