Short answer - Yes, you've heard from one already, and other folks here have also reached the 10 year mark. And while I'm not aware off-hand of anyone here, published longevity studies have certainly included patients at the 20 year mark as well. 2-5 years is more the anomaly, as Emu said, although the upper range of that potentially less of an anomaly for someone in their 20s.
Long answer:
While surgeons do this all the time, it's a mistake, I think, to ever say that a tissue valve will last "x" number of years, certainly not without speaking to age groups, and even also when a given age group is identified. The reason I say this is this: even in a best case age group (for analysis puposes, call it age 60 - old enough to have good longevity odds but young enough to maybe live long enough to prove it) there is still a wide range of longevity represented by individual patients. A very small percentage may have only lasted 6 years in this age group, but the vast majority have lasted into the 20 year neighborhood.
So, there might be approximately 10% odds a tissue valve would fail somewhere between 6 years and 15 years in this age group, but 80% odds it would last 20 years. Now, I'm being very big picture here with my numbers, so forgive me and bear that in mind, but they are loosely in the range of some of the proven tissue valve models that have been studied. My point here, though, is not about exact numbers, but that tissue valves longevity is better seen as a range of probability, not a defined "average" number of years.
In the younger age groups, the range of probability certainly shifts, in some ways the inverse to the above. The forecasting also becomes even harder, because many less patients have been studied. Then, for any age group, add the fact that most of the currently used valves have been in use for less than 10 years, and it becomes even more difficult.