Yes, it ends, but it is so painful while it is happening. It is heartbreaking to watch a parent with a zest for life reaching the end. I am tearing up right now remembering my own mother clutching at those last days of life. I am continually surprised by how the grief resurfaces.
Take good care of yourself during this time, OP, and know you are doing a good thing, giving your mother all the love and comfort you can during the end of her life. Be very gentle with herself after the end, because while you may feel very fragile for a long time afterwards. Lean on the people around you.
Sending you hugs.