The FDA several years ago issued a report regarding tablet medications, after doing research on behalf of the US Army. They found that the manufacturer simply is highly conservative in giving a year to two years from date of processing for an expiration date, when the medication doesn't start breaking down for approximately 15-20 years. In other words, as long as it is in tablet form, the medication will still be equally potent even ten years after you filed the prescription.
It's for this reason that soldiers get tylenol and such from the 1990's administered to them when they have a headache (to avoid constantly throwing out and replenishing stockpiles of medications) even to this day.
Now having said that, where are you storing your medications? If it's in the "medicine cabinet" typically found in a bathroom, you may as well throw them out, as no medications in tablet form should be kept in such an environment due to the humidity from the bath and shower causing tablets to partially dissolve from the water vapor.
Another thing is that you shouldn't stop, then resume medication at a later date without consulting a healthcare professional. Antidepressants are amongst the groups known to loose efficiency if the user stops taking them for a period of time (as the body has a chance to create a resistance to the drug if it gets a sufficient break). Remember, your body doesn't want the medication in there, and sees it as a toxin which it tries to filter as quickly as possible. Which is why you keep having to take it on a regular basis, to prevent the body countering it.