It's always the best to update the firmware before installing the OS. This way, you don't risk losing data unless there is already date in the drive that needs to be backed up.
George is right. Generally speaking the firmware update and background programming purpose will help the SSD perform better. You should always backup your data before proceeding with the procedure as it was already mentioned, this way you'd be able to avoid the headaches of data loss. If you need assistance with the update process, you can refer to this guide: http://www.storagereview.com/how_upgrade_ssd_firmware
In the event it does happen to erase the drive, the reinstall of the OS and programs will reduce the life. Overall a 1tb ssd can handle 100tb of writes on average, so you will lose up to 1% of the life if all your data is lost. But in most cases no data is lost and therefore no life reduction since firmware is written to a separate part of the drive than your data.
A TLC or MLC 1TB SSD made by a good manufacturer can absolutely handle not just 100TB of write, but more than 1000TB of write. One website did such tests, and most drives can handle at least 400TB of writes before they fail. Many can do 800TB, and the best one, a Samsung 840 Pro 256GB drive could do more than 2000TB of writes. Those were SSDs with MLC technology. SSDs with TLC technology can do less but shouldn't be far off I believe.