100/70 mmhg BP is absolutely normal. And no need to check daily because it fluctuates a few mmHg all the time, and note that BP is not defined by age. For all adults, it should be less than 130/80 mmHg.
Normal blood pressure is considered to be between 90/60mmHg and 120/80mmHg. High blood pressure is considered to be 140/90mmHg or higher. Low blood pressure is considered to be 90/60mmHg or lower.
Quora