QUOTE (Tymeaus Jalynsfein @ Jun 28 2015, 06:46 PM)

Once you have successfully cast a spell, you can sustain it outside of Line of Sight. LOS requirements are only for Targeting of the spell...

That is also how we played with it in the former editions.
But I'll have to persuade my GM that it is like this in 5th: do you have a reference to where the rule is?
The only thing I can find is in the core rulebook on p. 283:
"
Duration: This describes how long the spell’s effect lasts. Instantaneous (I) spells have an effect that happens and then fades, while Sustained (S) spells last as long as you keep them going".
But I guess that would probably would suffice...
A.