Tzvi Stern asked:
Practically, why is there the halacha that one can assume his wife is tahor if he left town when she was tahor (as well as other calculations)? In any case he would need his wife's consent for relations, so she would inform him as to her status!
Tzvi Stern, RBS
The Kollel replies:
Although it is certainly frowned upon, one may have relations with his wife when she is half-asleep, and under such circumstances she would not be able to inform him of her status.
D. Zupnik