Most likely just an irregular period.
I usually change it when I do the oil. But it would depend on how much you drive and how you drive. If its no longer green/orange probably time to change it. The cleaner you keep it the better the run.
After a period of time it decomposes and after long period of time it may even become dirt.
If the time period is increased, the frequency decreases inversely proportionally. This is because frequency is the reciprocal of the time period. So, as the time period increases, the frequency decreases.
Nothing happens seven years after a girl has her period. There's nothing specific about this length of time.
It gets cold
if at the same time? They Die.
They atrophy
they become flabby and smaller.
When something happens over a long period of time
They Will die
now 50%h20 and 50% antifreeze