Normally, if you are not preparing to wear, it could be soaked in the lenses solution for one night. Even under the circumstance of spare, the solution must be change every 3 days. You'd better control the period of soak in the solution while keeping them sealed in the containers. The solution must be changed after that. It will be getting hard without solution soaking. Then it will become crisp and easy to be broken, as a long time without solution moistened, the crazes will be appeared on the surface of lenses which is hard to find with naked eyes observation. It will damage your eyes with abrasion. You must get rid of it when it gets hard without water.
In general, you'd better keep your contact lenses soaking in the provided lens case for at least 6 hours. No matter whether the pair is new or not, placing contact lenses into case and let them soak overnight is totally enough. What you should keep in mind is that the lenses should be kept in liquid environment rather than the drinking water. In some cases, after leaving water for a short time, if you put them back into the contact lenses liquid, they may be soft again. In contrast, for long-time without liquid, lenses will be dry and hard, which means you cannot use them anymore. More importantly, it is extremely essential to enzymatic clean your contacts if you want to extend the life of your contact lenses.
Generally speaking, a night in contact lenses solution will suffice. For your information, I usually soak mine for at least 10 hours minimum. In so doing, contact lenses can be retained in optimal moisture and will become more comfortable to wear. If you donâ€™t know it all, the description on you contact solution box will shed some light on the maximum length of time for soaking. If you are so unfortunate as to forget to soak them, they will, with no doubt, become dried and stiffened and cannot be used any longer. So do make a point of checking whether they are soaked or not every night before sleeping.