My first Time Machine configuration on my iMac. Having internal SSD it´s a step backwards to connect spinning external hard drive for back-up. I lean towards the LaCie Rugged USB 3.0 / Thunderbolt SSD. But I´m not sure if an external SSD is the right choice with Time Machine. Since Time Machine continues to back up, the drive will eventually fill up over time. But I have read that I should avoid filling up an SSD, since writing the same sectors will reduce lifespan dramatically. ???