I think you made have made some errors.

15 series - assuming all 26 episodes and ~25-30 minutes each.

~650 minutes per series or ~11 hours.

11 hours to finish 15 series [watching all at once].

1000/15 * 11 = ~734 hours.

I think this should be right.

1 month assuming I stay up 24 hours for that one month to watch. Highly unlikely and very dangerous so lets go to, lets say, 15 hours of viewing a day. It should take ~49 days.