I created 2 routes from IAH-LHR. Both ran all week. Flew them for a month or more, then decided I really needed to leave space for a-checks, so had to cancel 1 day of each route.
On the 25th & 26th of July, I received warnings to say I was 1 month away from losing my Wed 13xx LHR slot, and my Thur 14xx LHR slot.
On Aug 4/5, I cancelled all my routes, and recreated them as a 7 day schedule. Midday on Aug 5, I received a warning to say I was one month away from losing both my Wed 13xx and Thur 14xx LHR slots.
I'm not waiting to check when I actually lose the slots. I assume it would be on Aug 25/26, and not on Oct 5, as implied by the most recent warning.
Seems like taking the 1310 slot, and creating a 1350 route, has generated an extra, incorrectly timed, warning.