I noticed this a while back. Personally I don't bin absolutely everything. The key ones to keep in constant rotation for me are cumin, coriander, paprika, garam masala, and tandoori masala. Spice mix never lasts long enough to go off.
I find that chilli powder, cassia, bay leaves, and turmeric last longer and keep their potency.
Curious to see what other do as well, as I am convinced that fresh spices are critical to good results.
-- Josh