Is it a burden to our teenage son to have my mother-in-law live with us?

We have been caring for my mother-in-law in our home for about 6 months now. She has ahlzeimer's, and is slipping downhill pretty fast. We have pretty much put our lives on hold to take care of her, moving her in here, cutting back on work hours to take care of her. All pretty much without any prior planning for this, or training. You do what you have to do.
My son is 13, and 13 already sucks, but even more so when your 'crazy nana' has moved into your home. He has been awesome, loving, compassionate and supportive of having her here, but I know this is really wearing on him. We do encourage him to have lots of extra activities to keep him busy, sports, church, friends, etc. but I know the longer this is the norm in our home, the harder it is. We are a close family, we talk a lot about the situation, and process things together, and I'm really proud of my son. But can't help but worry that we are scarring him for life. Anybody relate? Any ideas?