You could put 3 individuals I1, I2, I3, I1 starting from 0, I2 from the average (ex 1000) and I3 starting higher (ex 2000), so average is : (0 + 1000 + 2000) / 3 = 1000, and looking at what happens during 80 years (life expectancy).
- you could count those accounts in other 3 colums in % of the average (or in number of basic incomes which is yet 5% of money supply), so in that point of view the account won't go to infinite. You will have then 2 different ways to count : quantitative (like the one you used here) and relative (in % of money, or basic income, or average).
You can see a calc file for that here (see the 3 spreadsheets to see all of them). It has been analysed for OpenUDC/uCoin project in 2014 and in 2013.