Should several books be in progress at once?

Depends when you read. If you would only read at home I would recommend to read one and finish it. I don't always follow this rule because sometimes I'd have quite a dense book which kept me awake.
So if you read before you go to sleep I'd pick an "easier" book.
On the other hand while commuting to work, I'd always read short stories.

When I think about it, no. They aren't actually in progress, I'm abandoning the first for the second.

There is an exception, I have a few books I work through slowly and deliberately. With those, I like to lighten things up between readings of the heavier stuff.

So I've changed my answer to yes.

I feel you could read multiple books at once. As long as you are consistent you’re mind will remember things within a few minutes of rereading something. Personally, I can have maybe 2-3 books going at one time

Should? You may read different books at the same time. I do that, I have 2 or 3 in progress, and I choose one depending on my mood.

No absolutely not necessary. Actually in fact it will only encourage you to set yourself up for failure, whoever, has decided for themselves that they really need to do this for themselves is unbelievably screwed up in the head to the point of really unusually abnormality.

Why not? Reading is good for your mind and gives you other people’s perspectives. So, I recommend reading whatever interests you, especially those which help you grow spiritually.

I don’t know about should. I know I have about 7 books with bookmarks in them lying on my bedside. And I enjoy harbinger a choice every evening. But I limit myself to just one fiction book at a time otherwise I get the storylines all mixed up. Just read what you enjoy! And if you can follow multiple fictional stories then do it. If you’re really excited about one story you’ll gobble the whole thing up without interruption from other books anyway.