Very true, judging by the threads praising this product up over on DW, I should imagine it'll be at least 2 years, rather than up to 2.
[geek] Apparently it works by making a covalent bond with the plastic of the grille. It does so by swapping ions over or summat so in effect the C4 actually becomes part of the grille itself, the reason I guess why it is so long-lasting compared with other products. [/geek]
I'll post some 50/50 photos up when it decides to arrive!