I set up a sheetsheet, first column just a long string of random numbers between 1 and 50, second column, a test to check how quickly you see each number. After about 100 data points I got bored, at which point I had an arithmetic mean of 220, and a standard deviation of 51.

So, 220 +/- 51 is about the number of parts the majority of users should require before obtaining a full set bumuming a normal distribution. A minority will see results outside this range. The maximum I saw was 372 Log in to see images!