Are we advised when our premium subscription is about to expire, as I believe mine is about run out anytime now.
Normally yes. You will get an email saying that it's going to expire, and one when it does. Unfortunately we seem to be having issues with our email system, and they do not seem to be getting sent out.
We are looking into it.
(warning: tongue-in-cheek reply ahead!)
You're a Premium member that sounds like he knows his way around Todoist, so check on when your Premium Membership expires (Gear icon | Todoist Premium link), and add 'Renew Todoist Premium Membership' as a Task in Todoist (you could even set a reminder a week ahead of time!). :)