I assume the reason for the long delay between entering the ballot and getting the result is that they need to get GFA applications in and deferral places and charity entries etc, so they know how many places they have to allocate. In contrast, the Great North Run announce the results a few days after the ballot closes for entries.
I'd be interested to know what the evidence is for the shaping you describe? Phrases like "it is generally accepted" (in the passive voice) alway make me question the received wisdom.
For obvious reasons I think it would be far fairer to shape the outcomes to favour those who have entered unsuccessfully a number of times (like the OP). One simple and transparent way I've seen suggested would be "multiple entries" for those who have entered multiple times. If it's your second year you get two chances of winning, or twice as much probability of winning as a first timer, and so on. It resets if you miss a year or get a place. I realise they can't honour the five year rule any more, but this would help make things fairer.
Incidentally, it turns out I got a place this year! My second year of trying (and bequeathing, although there was no mention of whether I got my place from the raffle or not). A lot of friends were disappointed, so I know I'm exceedingly fortunate and I'm also very chuffed , if a little apprehensive!
Boring probability lesson, while I wait to go home and check todays post.*
Lets imagine the odds for each entry are 1 in 5 (as is commonly suggested).
On your first entry the calculation is simple.
1 in 5 = 0.2 or a 20% chance.
On your second entry you don't add your "20%"s together to give 40% (because that would guarantee a place after 5 entries which is wrong). And you don't multiply the 0.2 values (because that would lower the probability which is wrong). We multiply probabilities when we want the probability of x and y happening. 0.2 * 0.2 gives the probability of getting a place in year 1 and in year 2 (4%). Instead you can think about it like this. What are the odds of notgetting a place in year 1 andnotgetting a place in year 2? 4/5 * 4/5 = 16/25 = 64% . So the odds of getting a place at least once in either of the two years of entry are the opposite of that, 36% (because the probability of getting a place plus not getting a place has to add up to 100%).
So after 1 entry your chance of getting a place is: 1-(4/5)=0.2=20%
After 2 entries: 1-(4/5*4/5)=36%
After 3 entries: 1-(4/5*4/5*4/5)=49%
4 entries: 59%
5 entries: 67%
6 entries: 74%
7 entries: 79%
8 entries: 83%
9 entries: 87%
10 entries: 89%
So (again, assuming it is about 1 in 5 each time) after 10 entries, the chance that you were successful at least once is 89%. After 12 entries you had a 93% chance of being successful at least once, or a 7% chance of STILL not getting a place, about 1 in 15.
But of course you're never guaranteed a place even after 100 entries. And, perhaps confusingly, even after 9 fails (or 99 fails), the chance on the 10th time (or the 100th time) is still 1 in 5 or 20% (like Sussex Runner NLR says). The unlikely thing has already happened by then (as Keith says).
* although I bequeathed so I'll probably have to wait a bit longer...