I buy the large shampoo and conditioner containers and always run out of conditioner before the shampoo. While in the shower lamenting the fact that the conditioner bottle still had a little residue inside and would get wasted, I added some water and shook it up well. I extended my conditioner for at least 5 more hair washings, so hang on to your empty container for the next big tip.
My new tip is to buy only the conditioner on your next trip and using the previous bottle (now empty) transfer half of the new costco bottle’s contents into it and add water to fill up to top and give it a shake. Then when ready to use the new bottle you purchased, add more water to fill it the rest of the way up and shake. This is more than enough conditioner for your hair needs and I have still got soft and shiny hair, with no complaints. You will now have two full bottles of conditioner and will be ahead of the game as far as price goes.