Baneat wrote: After using half a pound of el cheapo cafetiere stuff I bought half a pound of lavazza espresso stuff, which is very nice.
Taste in coffee is, indeed, relative and VERY subjective. If you like the Lavazza, that is fine, but it is on the low-end as far as taste goes (IMO), and (if I may be so presumptuous as to dare to speak for the majority here) I would say that few if any of the folks in this group use that coffee. Look at it this way- you may like a fast food burger at your favorite restaurant with a large clown out front, but compared to a steak at a nice restaurant, the burger is just dog food. You owe it to yourself to get a steak... life's too short to drink bad coffee.
To keep this stuff fresh, I have it in an airtight container in the fridge. How long will it take for this stuff to not taste as good as it does now?
I could give a whole list of smart-a** answers,

but since the coffee had little to lose after the first day when you opened it, it will last for a while. How long depends on your personal tastes, and ability to sense the changes in the coffee. Maybe a week- maybe a month - maybe a day.
I'm not sure if you count it as espresso but it does say it on the front, and for 1 pint of coffee (a big french cup measured out to 1 pint) how many cm3 of the powder do I use?
Espresso is a beverage. it is created by forcing water, under pressure, through finely-ground, tightly packed coffee. There is no such thing as "espresso beans" or "espresso roast." You can roast and blend coffee to be used for espresso.
The amount to use is the amount that tastes good to you. ABOUT one coffee measure (1.5TBS) per 4 to 6 ounces depending on how you like it. 1.5 T is about 22 CM3, so for 16 ounces of water, that would be four, 4 ounce cups, so 4 x 22 = ABOUT 80-90 CM3...? I think....???
