TS3005 Timer End of life...what should I do for an ultra low power astable?
You could use a DS1341/2 to generate a 1 Hz signal ...in addition it could be your main crystal controlled timepiece. It draws less than 500 nA @ 3 V. 

You could even use the new DS2417 which draws less than 200 nA @ 3 V and the 1-Wire interface is much lower power than I2C. 

Since I assume you are using an ATMega328P, the 1 Hz signal can be a wakeup interrupt along with any button presses.
If you are doing something like Chronio you should make sure to read Gammon and Morissey on deep sleep with the ATMega328(P), they are very useful research.