This is getting off-track, but while the pitfalls of two relevant characters out of potentially many are obvious and only excusable due to technical limitation of the platform, insisting on more than 40 relevant characters is likewise contraproductive. Who (which human) will readily distinguish two character strings more than 40 characters in length sharing the first 40?

I feel often the need to remind programmers, that they don't write code for the computer. The computer will make it obvious, whether it understands you or not. You write for the poor sod tasked to maintain your code three years from now, when you're at your next gig.