The 555 does not produce times longer than about 60 minutes and a new chip on the market produces times up to 1,000 hours. It is called C005.

Here is the prototype where we tested the chip:

Back of the timer module showing the two wires for the pot.

Connect the two top pads to produce 1 to 10 hours

A kit is available for $8.00 (plus postage) and comes with all components and a printed circuit board with all parts clearly shown on the overlay.
The pot is marked with 1 to 10 hours and this will be ideal for most applications. The tactile button starts the timing and the buzzer sounds when the time is up. Two output pins are also provided on the PC board to connect to other devices to turn them ON.
The output of the board turns ON a device such as a relay, after say 5 hours, and the contacts on the relay will turn the device OFF. The buzzer on the board will let you know the 5 hours is up.

• The project is connected to 3 x AA cells (4.5v) (in a battery box)
• Consumption when timing: 100uA
• Output: pull-up 3mA pull-down 30mA
• Connecting the pads at P1 and also the pads at P2 increases the delay by 8 times, making the timing up to 80 hours. (but don’t let P1 pads touch P2 pads). Changing the pot to 20M creates 1,000 hours.

email Colin Mitchell: colin@elechelp.com for payment for the kit via paypal.