I once rented a board to a Japanese tourist. He told me how he'd been surfing for 10 years. He then asked " what's a good board? ". I said "shouldn't you know since you been surfing as long as me ". The wife told me later that he comes on vacation once a year for a week, and that's the only time he goes surfing. So basically he has surfed for 10 weeks in the last 10 years.
One should not gauge your surfing level by the "years" but by the seasons you surfed. Some areas you can only surf half the year. In Hawaii, surfing for 1 week equals 1 month for a surfer in Japan. Maybe we shouldn't even ask, because it's more quality than quantity that matters. But saying you surfed 10 years when actually it's just 10 weeks is misleading.