It should go back to it's original length unless the bung has been pulled up the pole section but if not there's two ways of doing it:
First check to see if your bung has slipped up the pole by removing it and then re-inserting it. Once in pull the top of your elastic at the connector to stretch a few metres of elastic out and position the bung.
Then if the elastic is still too long....
...Replace the bung with a 'Winder Bung' and wind on a few turns of the elastic to re-tension it as required. This method is the better one as it allows you to increase/decrease the tension in the elastic at will
Or... Re-tie your elastic at either the connector end or the Bung end and remove the unwanted elastic
It all depends drm... on the type of elastic you're using. Some of the cheaper elastics can take longer whereas pure latex ones are more 'active' and then you've got the hollow elastics and Hydolastic
Try tightening your elastic up slightly and see if this makes a difference
Also, regardless which elastic you use make sure that your bush is big enough to allow free passage of the elastic back into the pole. If the elastic just fits and you've got the slightest bit of grime on it, it will stick in the bush
Also don't forget you can lubricate your elastic with several types of ready made lubricants or make your own using a mix of hair conditioner and water
Put it into a small squirty bottle and apply a little now and again into your top sections and pull the elastic through it to give it a coating
Don't forget though that over a period of time the lubricants can also glug up the inside of your top sections so every now and again give them a flush out with warm water to clear any build up - you'll find using the shower hose does this just fine, remove the shower head and flush the sections out with the hose and warm water 
By the way perhaps someone could shed some light on how you are to know how many sections need elasticating and also whether you make it up as a telescopic section or put over ? Never really understood how to tackle it when elasticating a new pole.
Also why dont pole manufacturers provide you with a spare tube for your top sections as they know that once elasticated they arent going to go back in to the original pole ?
Dave, have been thinking of moving to the crows foot knot, but am a little cautious, as has the line ever cut into the laccy, and what is it like when you are snagged up, and have to pull for a break?
Hi Matt, we did have a few problems with the site but back up and running now
TT, so far I've not had a problem with line cutting through the elastic but some people do recommend Dacron Connectors as a way around this
Basically it is a small section of Dacron that is permanently fastened to the elastic and then the rig line is connected to this as per a crows foot
Being new to pole fishing i was wandering:
How do i keep the 'joints' of my pole in good condition?
Should i replace the elastic regularly or do i leave it until it suffers damage etc?
How much tension should there be in the elastic...should the elastic in the pole be just tight enough to hold the crows foot/stonfo at the tip of the pole, or should it be slightly tighter...how do i judge?
Thanks Dave for your info on elasticating the pole. I did tie a length of nylon string to the end of the bung. So i can pull the bung out with ease, if i need to tighten the elastic. Do you know of any product that i can spray on the pole, so as when i pack the pole up if its damp i don't have the sections sticking together. Which has caused me some problems. I have recently brought a maver resolution, which I've yet to fish with. Is this in your opinion a good pole?
There's that many poles out there at the moment it's hard to be able to have an opinion on them all but Maver, for their sins, do make good poles
As for keeping your pole clean, best thing I use is a can of Pledge, furniture polish
Every now and then take the pole into the shower and give it a good hose down. Undo the shower head and flush the sections through with warm water and then let it all dry - again the shower cubicle is a good place for this but it does help if you take your pole apart first as the missus generally doesn't like 13m of pole in the shower [8D]
Once it's dry, get a cloth duster and spray some polish onto it and then wipe the pole all over
Pledge is good for cleaning the pole plus it leaves a polished finish which helps repel water and therefore helps to keep the pole clean in use
It always helps to have a small towel, or beer cloth, in your tackle box and then if it does rain or you get the pole muddy you can wipe it off before putting it away. This is a lot easier than getting it back out again after every trip or finding it all manky and sticky because you didn't clean it between trips