Unless you use daily cyborg contact lenses, do not wait at the end of the day to remove your lenses and discover that you are all out of cleaning solution. What will you use to clean your lenses then? Have a ready supply in stock of contact lens solution to prevent such event from happening.
This is very important since you need to use fresh contact lens cleaning solution every time you touch and clean your contact lenses. Tap water is a big no-no to clean your contact lenses. It can contain impurities and infectious microorganisms that can hurt your eye and even eyesight.