I am thinking about using a custom domain for my blog, but I have been using the site as a home for my writing for a while now and have sent lots of links over the years to friends/family etc. If I update the domain, will those links all break? Or will the .writeas.com domain still redirect to my blog.
Your blog will always redirect readers to your current preferred URL. So if you switch from *.writeas.com to your custom domain, all those old links will continue working just fine!