How long should 100ml of contact lens solution last for?

I have just started wearing monthly contact lenses and was given some solution to clean them and store them in overnight, and I replace the storage solution every day. Using as directed by the optician, I seem to have got through the bottle in about 10 days. Is that normal? Or am I allowed to reuse solution which was storing the already cleaned contacts in? Thanks!|||Yup. ITs normal to go through them that quickly.