Interesting that.
When I got mine done, my AME, so that because I was under 30, it would last for five years, even though I'd be 34 then.
Then later my flight bag got stolen, so I had to get the medical re-issued by the IAA. They re-issued it with only a year 2 validity (i was still 29), so I queried it. They re-issued it with a 5 year validity.