I don’t leave any silence on loops.But,like Art said,always check loops back in back to see if there are any glitches/clicks.
In very rare occasions i noticed some clicks,i just faded out the last 0.25 sec (or less) and it looped smoothly then.
4 or 8 bars length is the most common formats i think.
Performance wise,P5 is doing very well for me.Frequent loop sales there.
Occasional loop sales in AS too.