Unless your Tablo is sitting on or under something that generates heat, or stuck in an enclosed space, it should be just fine.
We can actually check to see if your Tablo is running within safe operating temperatures, so if you have a concern please touch base with our support team: www.tablotv.com/ask-tablo
(One additional note - both Tablo DUAL and Tablo DUAL LITE have internal sensors that will turn the device off if temperatures exceed the safe operating range if - for example - your cat decided to sit on it.)