A few years ago, my Taekwondo organization (ITF-based if that makes a difference for purposes of this question) made the shift from point-break sparring (sparring stops after one side scores, resets to start and begins again) to continuous sparring (sparring for a set time period with no breaks beyond those necessary for handling fouls or injuries) at competitions. While I was not with the organization during the transition, many of the older members like to debate the merits of point-break sparring. This led me to wonder, what are the primary changes one has to make in terms of approach and style when shifting from point-break to continuous sparring?
The primary change is that daredevil / suicide moves now lose all interest.
All these moves, and more, are now begging for punishment much more than before, when a judge might decide to call a point and stop the encounter before retaliation happens.
This having been said, if you are doing continuous sparring without any kind of focused contact, then you might be inviting the windmill strikes: a lot of small strikes that don't really open you up, but also don't really commit to anything.
One of the major differences is stamina and cardio. Now you have to keep moving for the entire bout, and preferably keep the opponent unbalanced in some way (mental or physical or both). Better breath control is definitely required. In addition, you now also have to keep your hands up for the entire bout. That'll work your shoulders.
And finally (this is not an exhaustive list, but what I consider to be the main points from which everything else derives), point-sparring tends to easily remain on a straight line, like fencing. Continuous sparring forces you to shift around the opponent, otherwise you can easily get overwhelmed on a straight line only.
I believe that by changing the style, it helps to improve self defense as well as stamina. It helps in self defense as it simulate a real fight. It also helps in stamina as the fight is continuous. Therefore,I believe that taekwondo is not always focused on brute strength but also helps in thinking fast to either wear down their opponent or to be on the offensive :)
I agree with other answers here that cardio is definitely a factor. I have to disagree regarding more variation in technique moving from point-break to continuous sparring. I submit that, because the dominant form of competitive TKD sparring is Olympic-style sparring, that you will see less variation in techniques moving to that style. I believe that the techniques one uses in any sparring competition, regardless of style, will be the techniques that are known to point most frequently.
Granted, at the very highest level - the Olympics - you will see some amazing feats, but, often you'll see a lot of bouncing around and adjusting of equipment while each competitor waits for the other to make the first move. Even at that level, the repertoire of techniques and tactics is not really all that large.
The general flow of an Olympic-style match goes like this:
Generally, the defender has the opportunity to accept and incoming strike and immediately counter to nullify any points, or to get out of the way and bring an attack of their own. So, from what I've seen at competitions, there is a significant head game and waiting game going on. At first it involves lots of bouncing and adjusting of equipment. Then someone throws a fake to get the other person to commit. This behavior continues until someone commits, or until the ref calls timeout and fouls one or both combatants for not attacking (this particular foul is relatively recent and I believe is a direct result of the rest of the world getting really bored when watching TKD tournaments).
The adjustments to mindset/training:
There are other factors, such as using the ring and the rules to force fouls or time-outs, etc.
From my experience point-stop sparring can really lead to 'tag'-like situations, where both opponents are only trying to touch eachother as quickly as possibly with no regard for what happens after the attack / counter-attack.
One of the most frequently used techniques in TKD point-break is the jumping back fist, after which the attacker basicly falls over the defender and counts on the fact that the match is stopped to check if there was a score.
You'll find that training for point-break does have it's merits though. There should be a strong emphasis on explosiveness and accuracy. It also teaches you to see openings really well. On the other hand the drills are focused on single attacks/counter-attacks and on a limited set of techniques. There's usually no point in training a double-punch combo followed by a round kick to the belly button for example.
Continuous sparring is often the favorite with people who believe 'sparring' should mimick a real fight as much as possible. There's a lot more contact and both participants are therefore forced to keep engaging and exchanging. You'll find a lot more combinations being thrown here and a lot more styles of fighting can be succesful. Emphasis during training is on a greater variety of techniques and combinations and the sparring drills are different as well. You'll see that condition places a big role in this form of sparring as well.
Personally I have always favored the continuous style of sparring and found it the most rewarding. That being said I believe you should always try to learn from what other aspects of the sport have to offer as they will almost always allow you to grow as a competitor and/or martial artist.