I have 2 problems with premade curry powders Firstly since they are already ground, the oils which give them their flavour evaporate quickly - after 6 months you may as well put sawdust in your food (this applies to individual spices which are ground as well), so I generally buy whole spices which keep much longer. Secondly I like to each dish that I make a new experience, so generally I make up spices for this dish that I am cooking. I do have small amounts of curry powder and garam masala that I have made up to use when time is tight. Recipes for curry powders