It may be worth noting that a regulator keeps voltage within acceptable limits, it doesn't keep it at a constant value. More revs will produce more voltage than a low idle will, everything gets a bit brighter, and the regulator stops it getting too silly. 14-and-a-bit volts is quite a common reading at ~2-3,000 rpm, you're likely to be a bit lower at idle.
Frankly I wouldn't worry unless there are other symptoms, or the bulbs are going from seriously dull to blinding, and keep getting brighter the higher you rev.
FWIW, I think Lozzo's diagnosis has got some substance to it. Do that
Jambo