you need to dip your case into boiling water instead of boiled water for at least three minutes, since the boiled water is allowed to cool as contamination and bacterial regrowth can occur if left.
The other concern would be cases that come with a peroxide neutraliser (normally a silver or black disc at the bottom), or cases with an antimicrobial coating on the inside, which could be damaged by boiling. I would consult your ECP before changing from the prescribed cleaning routine as it can cause unintended consequences. Normal advice is to follow the manufacturers instructions for your cleaning solution.
But I have to ask, what's the point? Contact lens cases aren't exactly expensive, you can usually get them included in with your solution. For the extra hassle and risk involved in sterilizing the cases and deviating from the manufacturers instructions.