I replaced the blades on a nine-year-old Mini Mazzer grinder, using genuine burr blades from Di Bertoli.
The blades were easy to fit, following the instructions of numerous Youtube demos, and the result was instantly visible - fast, regular grinding.
The price at Do Bertoli was far cheaper than the major parts distributor I usually use, and the shipping was reasonable and quick.
In short, if you've had your grinder for a while, consider replacing the blades - and look no further than Di Bertoli.