It would be very difficult to do a proper experiment to test this theory and I don’t know of any evidence that washed sperm does not survive as long as unwashed sperm.  In our laboratory the sperm is prepared using a sperm washing media which has been designed to give the sperm all the nutrients they require to maintain their viability.   Ovulation is determined using predictor kits that monitor the level of luteinising hormone (LH) in urine.  The kits are designed to be used once a day.  If you test more frequently that this it can give rise to a spurious result.  Alternatively the LH levels can be determined by daily blood tests.  Scans are usually only used in when drugs are administered to achieve induction of ovulation.