Actually, one way to avoid that is to use alphabetic characters in addition to numerals. In that way each position in the code can have upto 36 possible values. Remember that the decimal (base 10) number 1000 convert into binary (base 2) looks like 1111101000 but converted into hexidecimal (base 16) it is represented as 3E8 and in a base 36 system it would be RS.

I'm not suggesting that we use a base 36 system, just that there are ways to shrink down the length of numbers.