I find it incredibly disruptive every time this page comes up and it's never completely capable of restoring my tabs. Is there any way to disable it so that it will instead update when I choose to restart Firefox?
When I finally got tired of them crashing my browser at random times I took the time to stop them.
You can change the addresses that it uses to check for updates in the about:config. To be sure though I put all of those addresses and IP's in the hosts file to make sure there could be no contact. Now my firefox updates when I update my machine. Some of them may not be mozilla specific but all of them are blocked by me.
I got this list by using a squid proxy on a VM to log all addresses firefox connected to and watching the logs as firefox ran with no sites loaded over a two week period.
You can use the list below to search for keys in the about:config to change. Or you can just put these in your hosts file.
This is my list
127.0.0.1 safebrowsing.googleapis.com
127.0.0.1 push.services.mozilla.com
127.0.0.1 incoming.telemetry.mozilla.org
127.0.0.1 detectportal.firefox.com
127.0.0.1 img-getpocket.cdn.mozilla.net
127.0.0.1 region1.google-analytics.com
127.0.0.1 contile.services.mozilla.com
127.0.0.1 mozilla.cloudflare-dns.com
127.0.0.1 contile.services.mozilla.com
127.0.0.1 versioncheck-bg.addons.mozilla.org
127.0.0.1 content-signature-2.cdn.mozilla.net
127.0.0.1 helper1.dap.cloudflareresearch.com
127.0.0.1 dap-02.api.divviup.org
127.0.0.1 shavar.services.mozilla.com
127.0.0.1 aus5.mozilla.org
127.0.0.1 versioncheck.addons.mozilla.org
127.0.0.1 firefox.settings.services.mozilla.com