I worry constantly about losing my mom. I am 21 years old, I lost my father when I was 20, heard a loud thud sound and ran upstairs with my mom and we found him dead...he was 42.
It also scares me that because him and I are so alike that my life may be half over just as his was when he was 21.
If I lose my mom I'm fucked, I'm 21 on disability and on a Suboxone program. I wouldn't be able to make it myself. I try and talk to her throughout the day, and spend time with her...when I find myself getting frustrated with her I always step back and take a breath, just try and realize it's not worth it.
I feel like things with my dad are so unfinished, he was an alcoholic and drug addict, 2 weeks before he died the swat team is shutting down my street and raiding our house to collect his guns, then he goes to rehab, he's out of rehab for a week and dies. I was still angry at him, and yet I felt bad for him and always wanted to help like always.
I would say try to resolve any lingering issues now, and take a step back when aggravated with your parents and just remember they are doing the best they can with you, as you are trying to do with them. Maybe they were abused as kids, or weren't shown love in the way you would like them to, so it's hard for them. Now's the time to find out all these things, of course that is depending on everyone's willingness to share and verbalize feelings.
I know this may not all pertain to you OP, since you said your dad has Alzheimer's...so you may not be able to accomplish these things. If he does have moments where he can remember or something, maybe try and get what information you can out of him, as to where paperwork is, or questions you may want answers to. If things are too far gone, then you need to now do what you feel is right.
If you can make sure you know where all appropriate papers are, will, final wishes, insurance policy, etc. I know no one wants to think of these things, but it's so much worse being lost trying to set up a funeral, etc, with no clue where to begin and not knowing what your parent's wishes were while grieving and being depressed.
My dad always wanted to be cremated when he died because he was afraid of being buried alive, lol. So he is currently sitting in an engraved marble box in my mom's bedroom.