Hey BoJangle. The short answer is that the external drives are not meant for gaming and for such continues usage. Especially if the enclosure is not good enough, this might shorten the live of the drive. If you don't have enough SATA cables in your PC or if you are using a laptop, there might be more viable options if you do decide that you want to play from a drive which is externally connected, such as: a docking station and an internal 3.5" drive or if it's a laptop - an HDD caddy and a second 2.5 internal HDD.
Hope that helps. Let me know if you have any questions.
Boogieman_WD