Actually, an erection that lasts longer tahn four hours could be your last one ever.....EVER. The reason they tell Viagra (and other ED users) to seek medical assistance is that ...in non medical terms, the blood vessels will never be the same if you don’t make that bon...er...erection go away. You either need to ice it down or they poke it (no joke) to release blood trapped in the penis or it could be the last time you experience an erection.
The same effect is achieved when viewing a nude pic of Helen Thomas.
So, one would hear muttering under the breath about shrinkage or a piercing shriek, respectively, depending upon the necessary remedy?
The first time I heard that "precaution" in one of the ads they said "seek professional help". I suspected the folks in the TV audience who were able to stop laughing notified Phizer to change the advice.