Why are my strawberries keeping so long?
Most commercial fruit is picked before being completely ripened because once it is ripened it has a very limited shelf life, and strawberries are no exception. Strawberries ripen from the tip to the stem and a good indicator that a strawberry is unripe is a white ring around the stem area. 

Some fruits can be artificially ripened by exposing them to ethylene gas, but strawberries are not one of them, so it is not likely they are chemically treated as there's no gain. They may have had their color deepened, which is an artificial process but as I believe that's using Carbon Dioxide gas I'd hesitate to call them chemically treated. 

Out of season strawberries often come very long distances, in order for them to last they have to be picked well before they are at their peak. Once they are picked they stop developing and ripening, and nothing can be done to improve their flavor. If you are going to buy them out of season try and pick ones that are completely red as they have a better chance of tasting good, otherwise it's best to spend your money elsewhere.