We have some Tamiflu which was dated 2005 and my spouse Debbie was wondering if it was still useful, or should it be thrown away. Googling that subject turned up the fact that no really knows, but that it appears to be safe even if it is no longer effective. Tetracycline can turn toxic while on the shelf, but nitroglycerin and insulin only will lose their effectiveness over time, but according to a US Army study, nearly all other drugs if stored in a cool dry place will maintain their effectiveness for many years.
We store our pills low to the floor in a central closet wrapped in a down jacket, which generally means they stay a bit cooler than the overall house temperature of 69° F. I had a high/low thermometer in with those pills for a couple of years, in my old house, and the measured temperature never varied more than a few degrees. On those days predicted to go over 80° F, I would put an icepack one layer of down separated from the pills. It was an experiment as much as anything – I like to experiment with things. Our vitamins, which get consumed in a couple of months, are stored in a more convenient location, in the door of the refrigerator.
Aspirin may go bad if left in the bathroom. I have noticed that a bottle of aspirin will take on a distinct sharp vinegar smell over the years, especially if left where the straight sunlight will strike it for a while every day. Also, the bathroom tends to have some humidity at times and if the bottle is opened at a humid time some of the moisture will get into the pills and start a slow deterioration. The aspirin is probably still safe and only partially deteriorated, but the whole problem is avoided by keeping it in a dark cabinet with the lid on tight.
Keep your drugs in a quiet, dark, cool, dry and kid-safe place.