An SSD has a limited number of write/delete cycles before its performance starts to degrade, and defragging does exactly that. Deletes the data present and re-writes new data over it.
You should be fine unless its been defragging constantly. Modern SSD's have plenty of redundancies built in to minimize the damage of write/delete cycles and to keep performance running smoothly, as well as just being able to withstand many cycles. Under normal usage, an SSD will work fine long past its obsolescence.