Excuse me Mr Candy-Stripe, but the attached circuit has adjustable on/off times.
There is no mention, and as far as I can see no provision for long delays.
Mr. Candy Stripe? The text states that the design allows for "very long on times". The complete article can be found at Silicon Chip website. Go argue your point with the author there.
I think the "very long on time" is relative to the off time, i.e., extreme duty cycles are possible. There is nothing in the circuit that would extend the timing cycle beyond that of the "standard" circuit.
I did come across this circuit that uses a 556 (dual timer) .... from the same family, but technically not a 555. Still might be useful for anyone who needs long intervals.
I will stick with my Atmel 1200A version. One chip, internal clock and a dip switch. Just thought 2 x 555 I would free up that microcontroller for something else.
But a good find for future long delay timers for sure.