Any spices you have that are ground, powdered, dried and chopped, etc. -- these will lose their flavor at some speed after you've opened them. So, that year-old paprika or thyme? Not so tasty any more. There are two solutions to this problem:

1. Buy whole spices and grind them yourself. This is easy with, say, peppercorns and nutmeg and cloves, but you can also buy fresh oregano and thyme and other herbs and dry them and then chop or grind them yourself. A coffee grinder is a perfect tool for the grinding; I particularly like a model that Cuisinart makes, with a removeable metal grinding basket that's easy to clean.
2. Accept that your convenient, easy bottled spices will go bad, and use a sharpie and masking tape to label every bottle with the date you opened it, then throw out anything more than 6-8 months old.

Some combination of the above should help you make tasty food easily.

Also, keep those spices in a cool, dark place and they'll last longer.