I saw two quite instructive epee matches at the Swedish youth championships this last weekend.
Match 1: First DE round, score is 5-12 (or something like that) with less than a minute left until the first period break. Then, the fencer with the big lead starts to do fleche attacks, but they are not well prepared and the opponent is not caught off guard. Instead, he picks up the incoming blade, binds it in opposition, and scores on the incoming fencer. This repeats itself several times. From the outside, it looks as if the fencer with the big lead is trying to finish off the match before the period break, but goes about to do so in completely the wrong way. After losing quite a bit of the lead, the leading fencer comes to his senses and runs out the clock. After the period break, he does not do any more of that sort of fleche attacks, and instead prepares his attacks better so that the weaker fencer is well and truly at the limit of his ability to follow what comes at him, and therefore cannot counterattack or parry/riposte as well. The fencer who had the big lead before the period break eventually wins, but by a score of 15-10 or so.
Match 2: DE match where both fencers can be expected to be evenly matched. The match is indeed a nailbiter, the lead changes a few times, and there are long sequences of equal score. Eventually, one fencer works his way to a lead 14-12 with about a minute left to the next period break. That fencer also tries to finish the match off, and two attacks with insufficiently well laid groundwork leave the score even again, 14-14. After the period break, tension is high, but the fencer who clawed himself back to parity seems to managing his nerves a little bit better. After a short time in on the new period, the nerves break for the fencer who had the lead, and he does another badly prepared attack, the third in a row. The parry/riposte works, and the fencer who was down 12-14 has won 15-14.
Takeaway lesson: You do not need to force the issue when you have a substantial lead. Remember that time is working for you – your opponent will have to do something offensive, and therefore risk-taking, sooner or later. It might seem to you that the time never counts down to zero, but remember this: to him, it seems as if the seconds are ticking away at a frightful rate. As long as you do not do any unforced errors – or something else that is equally harebrained – you can simply defend your lead, and wait for the moment when he has a big deficit to overcome in a short time. Then he will be forced to take big risks, and you will find ample opportunities to score on them.
You might want to preclude the possibility of his coach coming with a fantastic suggestion that turns the whole match during the period break, but my experience is that such instances are quite uncommon. If you are so much better than your opponent so that you have build up a big lead already, then chances are that he is simply incapable of doing the actions that defeat you.