Using one FB post for Multiple Campaigns

I like the idea of making one post (or ad creative) on facebook page, and then focus my campaigns on the same post, rather than creating a new ad creative for every campaign.

Question to experienced advertisers - how does it impact the delivery of my content? For eg there is post which I am promoting to different audience sets in different countries - what would be the impact in delivery of impressions & ultimate cost?

What is the strategy that people generally follow? Should I make a new post (dark?) for every country or audience I want to the run the campaign for?

Every target audience has got a different taste and similarly every other product needs unique content based on it's type. It would surely matter in terms of likability of your adsposts and the CTR and ultimately conversions if you use the same content for all your products.