On difficult trails surely an extended tongue is a negative, increasing the wheelbase of the trailer. But for most uses, including most off-highway, a moderate extension won't cause a problem and will have some advantages.
After adding my rear bumper with swing-a-way tire carrier I couldn't open the rear hatch on my 4Runner because the tire carrier wouldn't clear the front of the Chaser. I had a 22-in. extension made at a local trailer shop. It was 'just' long enough to clear on level ground when the combination was perfectly straight. In practice during a recent trip I needed a couple more inches. I sold the extension and just had a 26-in. stinger/extension made which should give me the clearance I need for my tire carrier. The extension can always be removed the the trailer hitched-up close.
Like others have noted, the increase wheelbase is nice for towing stability and makes reversing much easier.
MoGas said:
What's the deal with extended tongues anyhow? It would seem like the trailer would be more likely to get hung up with a longer distance between the tow vehicles rear wheels and the trailer wheels.