Blinking an LED can't done with just passive elements. Interestingly, you can accomplish periodically blinking a light, with a resistor and a capacitor, if your light happens to be a neon discharge lamp. The reason a neon bulb will work and an LED won't has to do with their current-vs-voltage behavior.
In the LED's case, no matter what the voltage across it, some current will be passed. This effectively keeps the cap from charging up, as an operating point is established that is determined by the LED and the resistor. You'll just get a constant glow of some intensity.
But with the neon bulb, no current is passed until the voltage exceeds some threshold, which is the breakdown voltage of the neon gas. This allows the capacitor to charge up while the bulb remains dark. When the breakdown voltage is reached, the gas ionizes, and the energy stored in the capacitor is dumped through it, producing a short, bright flash.
Basically you need some device in the circuit that operates like an active device. To blink an LED, you need a couple of transistors (e.g., multivibrator configuration) or possibly a single SCR (biased to have a suitably low break-over voltage). In the case of a neon bulb, the bulb itself is the active device, having distinct conducting and cutoff behavior.
First off, your high-frequency flashing will give (at best) only a slight improvement in battery lifetime. The idea is that you can increase efficiency by driving the LED at a higher current, and while this is true for some LEDs, it's not true for all.
That said, getting a year out of a continuously flashing LED will take a rather large battery. Let's say that you're flashing the LED with a 25% duty cycle: that is, only on for 25% of the time. And furthermore, let's say that you are running the LED at 10 mA. Then (obviously) in one hour the LED will be on for 15 minutes. The total current drawn will be 10 mA x 0.25 hours, or 2.5 mA-hr. In one day, the total current drawn will be 2.5 x 24, or 60 mA-hr. After one month, it will be 60 x 30, or 1800 mA-hr.
Now for batteries. You can get rechargeable NIMH D cells that will give you 10 - 12 A-hrs of service, so you might think to get a year at lower current drains. However, http://data.energizer.com/PDFs/nickelmetalhydride_appman.pdf suggests that NIMH will self-discharge by 20 - 50% in 6 months, so that pretty much sets that limit.
A bog-standard alkaline D cell will have http://data.energizer.com/PDFs/e95.pdf a capacity of ~ 18 - 20 A-hr and in this application you'd think would give you about 10 months to a year. The problem here is that the lifetime is specified to the point that the battery voltage is 1/2 that of a fresh battery, and LEDs have a minimum voltage that they need.
So, what you want to do is "possible", but only if you can accept the battery size.
What you need to do is get some high-brightness LEDs, a cheap power supply, a DMM and some resistors, and experiment with the LEDs. Find the current level that gives you the brightness you need, keeping in mind that your installation may (or may not, you just have to think about it) be seen in bright light which will require more LED current to appear bright enough. Once you have a target current, only then can you start grinding out the numbers which will tell you how much battery you need.
For example, let's say you have 2 LEDs in series, and they draw 10 mA when on, and their forward voltage is 2 volts each. The LEDs will need 4 volts total. If you use alkaline D cells you can put 6 in series to get 9 volts, and at the end of life they will be putting out about 4.8 volts, giving you about 0.8 volts margin for your current control element. Assuming 20 A-hr for the cells, you'll get about 11 months.
Is that too big a battery? Well, there are other alternatives. For this long-duration application, http://batteryuniversity.com/learn/article/elevating_self_discharge indicates that rechargeable lithium cells (lithium-ion) are possible. http://www.electricwingman.com/power/a123-loose-cells.aspx has a single 20 A-hr cell. Note its size and weight.
Primary lithiums are also a good technical choice. http://www.onlybatteries.com/showitem.asp?ItemID=14509&vfpr=10.30&vfbr=Blue+Sleeve&vfcat=Electronics+Electronics+Accessories+Power+Batteries&vfsku=14509&vfbi=no_bid&sid=gpla&vfsku=14509&vfsku=14509&gpla=pla&gclid=CjwKEAjwuoOpBRCSy6yQm66J1g8SJABrXW48PiokBnHnnAVNcptv7FH19wDGumSYhbMnC9kQH9-IQxoCevPw_wcB is an example, and you could get away with one of them.
Best Answer
This is the most straightforward way that comes to mind. You could use another 555 timer (or an RC circuit equivalent) set to a period of 3 seconds and a duty cycle (ON-time) of 1 sec and OFF-time of 2 secs. The 555 output would be connected to an NPN transistor's (T1) base (standard CE config) to switch it on/off at intervals, according to its duty cycle. An inverter IC (or just another transistor) will also be needed. The supply pin of the 2-sec 555 will be connected to the collector of T1. The collector of T1 will also be connected to the inverter input, while the inverter's output should be connected to the supply pin of the 1-sec 555; this is so that both 555s are never ON at the same time. The outputs of both original 555s should be connected to the LED with a current-limiting resistor in series. A diode should be at each output to prevent current from flowing from one output to the other.
It should all work as follows: At first, the Master 555 output goes HIGH. During the Master 555's 1-sec ON-time, T1's collector is at 0V. Therefore, the 2-sec 555 is OFF and the 1-sec 555 is ON, because of the inverter. The 1-sec 555 generates its waveform within a second. T he Master 555 output then goes LOW, thereby turning off T1, and it begins its 2-sec OFF-time. T1's collector is HIGH, so the 2-sec 555 is ON and the 1-sec 555 is OFF, again because of the inverter. The 2-sec 555 generates its pulse. The Master 555 output goes HIGH again and so on.
Further tuning will be needed of course. An MCU would accomplish this with no more than a few lines and far lesser complexity so I presume you have a good reason for using this method instead.