Hi Anonymous - That's a great Question and Sho B gave a great answer. If there's an Assisted Living or Memory Care unit near you - see if they allow Respite Care. If they do, it's a great way to see if your Mother would be able to function there, and a way for both you and your father to have a break of a week or two.
Usually by the time someone wonders if it is time for help or Assisted Living, it is past time for it. It's a very difficult process, so be gentle both with yourself and your parents!