Sadly in the cases of severe dementia and psychosis, sometimes those spirits don't realize when they pass and remain very confused and frightened. I think those would be more in order of ones you wouldn't neccesesarily call on for aid or veneration right away. I would work to help them get clear, myself, and then once they've reaccustomed to the other-side that may be the time to begin working.
Actually, I have heard that you should wait 3 years before calling on ANY newly passed ancestor, so that they have time to adjust to their new existence. That makes sense to me personally, and so I've been following that guideline.
But there are soooo many different ideas about ancestral work, that it seems to me that if you are not part of a tradition that has very hard and fast protocol to follow, that you just go with what makes the most sense to you, and with what you get the best results with.
I've heard from some sources that ALL ancestors are to go on your altar, even if they were very abusive. I can tell you that there are several people who absolutely will NOT be on my altar once they pass. I've forgiven them - in that I don't let my past with them effect my current life - but I have no need of their influence in my space at any time. If I'm wrong, well then, the good Lord can slap me on the wrist when I get over there! But I would feel endlessly uncomfortable seeing their faces every single time I passed that altar, and that's just not something that I will allow to happen in my life.
So - do with what feels right to you and that works. You can always get further guidance from your ancestors about specific things they would like for you to do.
I like Martin Coleman's "Communing with the Spirits" - you should pick up a copy.

Devi Spring: Reader & Rootworker - HRCC Graduate.