[AaronBrown]

The average return on premium bonds is set by National Savings & Investments. I believe it is currently 3.25% per year. Of course, that's tax-free so it could be worth 4.06% to 5.42% to you depending on your tax bracket.

Your prize list comes to 72,750,000, which implies 26,861,538,462 of units outstanding, if my 3.25% figure is correct. By my calculation (which differs from the prior one because I'm not using 24,000,000,000 as the total outstanding), you need to wait 198 years to have a 50% chance of winning any prize 10,000 or larger.

There isn't really a lot of gambling with these bonds. Every 15 years, you expect to get one prize of 1,000 or more. During that time, you expect to get 43,875 total, almost all through the accumulation of 50 and 100 prizes. Even if the big prize is 1,000 or 5,000 or 10,000; it's not a huge difference over 15 years. There are 1,650 of those prizes, compared to the 37 that would really make a difference: 20 25,000; 10 50,000; 5 100,000 and 2 1,000,000. So about once every 15 years you get a 40 to 1 shot to make a difference.