I have wonderful memories of the first good grinder that I purchased...
Back in the ancient days of espresso there used to be one grinder manufacturer to rule them all... Mazzer. Things have changed a lot since then, but you'll likely still see the kingpin Mazzer grinder (the Robur... a beast of a machine) sitting in many of the cafés that you may frequent.
When I first started making espresso at home, I purchased a very cheap combi machine. The grinder was built in to a small machine which had one boiler which was used for both espresso extraction (below boiling point of water) and steaming milk (greater than boiling point). It was a very basic machine.
As I started to descend into the rabbit hole which is coffee, I made my first extravagant purchase... a Mazzer grinder... not the Robur the Mini Electronic. I can still remember the first espresso that I extracted using the new grinder, it was such a massive step up in terms of flavour concentration and viscosity of coffee. That extraction literally made me weep with joy.
There was only one issue that I had with the Mini Electronic... the grind process was very slow. It took about a minute to grind enough for a double shot (first world problems I know!). I started looking at ways to deal with this issue and I felt that the solution revolved around the burr set that was in the grinder. There's a very interesting little nuance with Mazzer Mini grinders that I needed to be aware of before purchasing an upgraded burr set though... there are two Minis that look very similar but are, in fact, very different. The Mazzer Mini Manual (which uses a doser mechanism) uses 58 mm diameter flat burrs, whereas the Mini Electronic, which I purchased, uses 64 mm diameter burrs. A small but very important difference.
After hours of research I discovered that the next grinder up the Mazzer line, the Super Jolly also uses 64 mm diameter burrs but with a more aggressive burr cut. The burrs themselves were compatible with the mounting in the Mini Electronic. I decided to try the Super Jolly burr set in the Mini Electronic.
Hallelujah! Faster (grind time was better than halved) and better grind... nirvana. That grinder and burr set still sit proudly in the kitchen of a friend and customer.
This wasn't the last time I decided to change burr sets, but those stories can come later!