Ethnic markets are your best source for both freshness and price for the spices of those regions. They have the highest turnover, so their stock is freshest.
Spices that come in tins in supermarkets.... you don't want to know what is in those cans bsides the spices! They are allowed a certain ppm number of "other things" like rodent hairs or bugs!
Besides, there's no real way to know how long those cans have been sitting on the shelves, or the warehouses before that.
If you don't live in an area where you can get to a good fresh source for dried spices and herbs, then online purchasing from a reputable source is your best bet. Buy only what you think you can use within 6 months. Things change after that. (Of course you can always share with family and friends
). And if you store your herbs and spices next to the stove or other heat source, their shelf life will be even less than 6 months. The heat will dry them out and change their character significantly.
I have had folks argue with me about these, but I know from experience of which I speak.
Penzey's, Spice House, Kalustyan's are all reputable on-line sources. I shop at Vanns
. If you live in the Baltimore area, I th ink you can go to their location.