What  are the setting for a short reverb and a long reverb say for example using the Sonitus reverb. Is it just the decay of say 1.5 for short and 3-4 for long

You'll likely get many conflicting answers to this question, because it varies with the song, the instrumentation, genre and personal taste.
 
Sometimes "short" means as little as half a second. I usually start with 1 second and adjust to taste. "Long" is even more open to interpretation, and might be anything from 2 to 8 seconds. I usually start with 3 seconds and adjust from there. What I'm listening for is a balance between smoothness and clarity. 

Try this - use a delay to answer this question.   
 
Open sonitus delay - and set it to host temp... and quarter notes.  After it syncs up flip it back over to manual, and it will give you a millesecond read out.  Somewhere probably between the 400 (for around 130 bpm..ish) to 1000 (for slower tempos of 60 to 70 bpm..ish)
 
Now - use this info to set your reverb decay times.   For example - a long vocal verb at 130 bpm might be double the 400 - which is 800, where the short snare drum guitar verb might be 400.   This way - using verbs will be congruent with the tempo of your track.  
 
If you use pre-delay on your verbs, say, 30-80 ms, just shave it off the decay time.  So - 60 ms of pre-delay at the 800 ms mark means set the decay for 740 ms.
 
https://www.youtube.com/watch?v=1Lmq6RDn5O8   Check out the creative use of predelay on the bass drum in this classic prince tune - the pre delay is set for an 8th note.  You'll also notice 16th note predelay times on guitars, vocals, and snare in this, with shorter decay times
 
 
Hope this helps!

Great tip David!

Thanks guys.