Earlier I used date and name permalink structure for my blogs. Recently I got information about SEO URL tricks and I made decign to change permalink structure to Post name.
But with this produced many issues. Like google search result will go to old site URLs and My blog links are posted on other multiple blogs. That links will be broken and redirect to 404. Also I interlinked my other posts with other posts. They will go to 404 page.
If your blog pages will not found then google site ranking will go down.