If we talk about SEO permalink is important part. SEO friendly permaink will make your site indexed better on search engine. If your blog already on google index you must becareful if you want change your permalink. When you change permalink with the new one, on search engine index still save your old permalink and when people click it, visitor will get error page. You will lose many visitor if you not fix this.

I just change permalink and i have solution for this plugin. I search for plugin that can do smart redirect and i found Permalink Finder plugin.

When you migrate from another platform to Wordpress, the canonical names of your posts may subtly change. Old links, including Google may throw 404 errors on your permalinks. In order to redirect your valuable links to the new naming structure, you will need some way of locating the poast based on the information available in the old link. Redirects links to index pages and keeps a log of recent 404 errors and redirects.

I try this plugin and work very good.