It came up on my phone last night. You can force a check with the pulley menu on the Settings > update page. I don't know how often it checks or if Jolla pushes a check. I suspect the latter, because I have seen it go seven days without a check, and last night when I looked 3.0.0.8 was there when it hadn't been yesterday morning. I think 3.0.0.5 was purely the early access, a/k/a beta, release.
I'm not in the early release program -- my days of being up all night to fix something have mostly passed. (Having said that, I am waiting for the battery to run down because the install is stuck before beginning because I forgot to uninstall an app that must be uninstalled before the upgrade, after which it will boot into 2.2.18, I can uninstall the app, and the process can begin anew.)