Do sun-dried tomatoes expire?
There are many ways of storing sundried tomatoes. If stored in oil, they last a really long time (because of the occlusion from air) and certainly 6 mos is okay if that is the case with yours.
If just dried and not required to be refrigerated, sundried tomatoes just continue to dehydrate as they age. Those can get hard as a rock, but you rehydrate and they are good. Those can get a stale after a few years, but, 6 mos. is okay so far as bacteria (that forms in moisture).
Because your particular package does not have an expiration date, I would say use them though they have been in your fridge after opening for 6 mos. if you see and taste no indication of mold or contamination. Same if they have no "best if used by" date.
To be absolutely sure, call or e-mail the particular
producer of your sundried tomatoes. Mezzetta brand does not have expiration dates, but often say that once opened, they may last just about 2 weeks. However, they add that if you see a white mold, then please discard. In other words, they may last longer than the two weeks depending on how they were handled.
(Have you ever opened a container of cottage cheese, used some, and then placed it in the fridge upside down to get rid of the air around where it was exposed to outside elements? That upside down storage keeps it fresher for almost 2 weeks longer because of the occlusion from air.)
But, you are right, if there is no sign of mold or altered taste to a tempered palate, they are okay, especially if when you used them last, you used utensils to remove from container and not just your fingers (as there would be more germs there).