Other people seem to have more luck than me, but I've only had two in the last two years, and they were both on European flights (one in the old "Real Business Class" days, one a couple of months ago when it was Europe Select). Had a couple of long-haul ones many many years ago, but none since.

My other half has been slightly luckier, he's had two or three long-haul ones in the last three years, including one in mid-flight when they needed to find a seat for someone whose audio system wasn't working (i.e., they moved him into Business Class so that the other person could have his seat). He missed out on the Business Class dinner, but at least he got his "huisje" for his collection!