"Purging" vs reaction: How long do you give a new product before giving up?

I have redness and p&ps, and very dry skin. I've been on a years-long quest for a moisturizer but every single one gives me p&ps after a week or so of use. I usually just give up at this point and retreat to using marula or argan oil, the only things I can tolerate. But I'm wondering if I should be giving products a longer time to see if it's "purging" or an actual rosacea reaction. Maybe I'm giving up too easily? For people who are also very reactive, my questions are:

  1. How long do you try a product before you give up on it?
  2. When you try something new, how often do you use it at first?

(Post inspired by the reaction I'm currently having to cicapast baume 😢)