i am assuming that you have a carbed cs, with mechanical pump, probably is too much of an assumption, normally is much better if you clarify it when you describe the problem, but lets think it this way
for such a setup, it is may own case, a week or even three weeks makes no difference, car will start at first attempt, but two things must be considered
my carbs have been recently renewed, so there are no or very little leaks in them, fuel does not evaporate so quickly i guess,
second, i added an anti-return valve in the fuel line just before the mechanical pump
my starting procedure in cold is aleays the same, first a milisecond press of the accel pedal to hear the butterflies clossing, then a brief kick of the accel pedal to the floor to inject the fuel from the kickdown pumps, and then remove feet from the scenario and start the car
so i would consider the anti-return fuel valve if you do not have it already,... ! ?