How do I make a trail stay for a few seconds after the object is removed/broken?

[StrawBMuffin]

Hi, I'm working on a modification to a squirt gun SWEP, and I managed to use a few tutorials to so far make a weapon that shoots a prop with a trail behind it to mimic water being shot from a water pistol. So far it works, but the only problem is that the trail doesn't die out after the prop fired breaks on collision, it just disappears. How can I make it so that the trail stays for about a second after the prop breaks?
Here's the code I used:
function SWEP:ThrowChair( model_file )

-- If we're the client then this is as much as we want to do.
-- We play the sound above on the client due to prediction.
-- ( if we didn't they would feel a ping delay during multiplayer )
--
if ( CLIENT ) then return end

--
-- Create a prop_physics entity
--
local ent = ents.Create( "prop_physics" )

--
-- Always make sure that created entities are actually created!
--
if ( !IsValid( ent ) ) then return end

ent.trail = util.SpriteTrail( ent,0,Color(255,163,128,255) ,false, 1, 0, 0.3, 0.0025,"trails/tube.vmt")

--
-- Set the entity's model to the passed in model
--
ent:SetModel( model_file )

--
-- Set the position to the player's eye position plus 16 units forward.
-- Set the angles to the player'e eye angles. Then spawn it.
--
ent:SetPos( self.Owner:EyePos() + ( self.Owner:GetAimVector() * 16 ) )
ent:SetAngles( self.Owner:EyeAngles() )
ent:Spawn()

--
-- Now get the physics object. Whenever we get a physics object
-- we need to test to make sure its valid before using it.
-- If it isn't then we'll remove the entity.
--
local phys = ent:GetPhysicsObject()
if ( !IsValid( phys ) ) then ent:Remove() return end

--
-- Now we apply the force - so the chair actually throws instead
-- of just falling to the ground. You can play with this value here
-- to adjust how fast we throw it.
--
local velocity = self.Owner:GetAimVector()
velocity = velocity * 500
velocity = velocity + ( velocity ) -- a random element
phys:ApplyForceCenter( velocity )
end