Vmo/Mmo is more a target limit in that the pilot is required to not exceed the value intentionally other than where authorised for training or test purposes. See
FAR 25.1505.
Short interval excursions of a few knots are to be expected on occasion and are not going to rip the wings off ... However, if the air be bumpy one probably would be well advised to carry a small pad below Vmo.
However, I have to agree with my colleague ... for a competent instrument pilot, getting the clacker should be an infrequent event.