One of the most infamous elements of Dragon Ball Z came about in the "Frieza/Namek Saga" arc. This intergalactic escapade involved Goku and the Z Fighters taking on the tyrant who had killed the Saiyan race. Said fight took quite a while, even if it logically shouldn't have.
The description of how long the battle against Frieza should have lasted notoriously doesn't match up with the length of the actual match. This may be explained, however, due to the location of said battle, with Namek being an alien world compared to Earth. Here's why Frieza's "five-minute" countdown made sense to take so long.
Namek Took Several Episodes to Blow Up In Five Minutes
During his fight against Goku, the evil alien despot Frieza remarks that the planet Namek is set to blow up in five minutes. Of course, the logical tension that this should have created is pretty quickly gotten rid of, especially considering that their dramatic battle doesn't meet its end for almost 10 additional episodes. Such a line is completely incongruous with the show's length, and it's become an infamous moment in Dragon Ball Z history, as well as for long, drawn-out fights for shonen anime in general.
The real-world explanation was that the Dragon Ball Z was catching up with the production of the manga, presenting the need for filler storytelling. This way, there was more padding added in, allowing the manga to progress further. Thus, the Goku vs. Frieza fight seemed to be a much more arduous affair. However, even with this idea, it's possible that the fight really did last for only five minutes due to it taking place on the alien location of Namek.
Time Works Differently on Namek in Dragon Ball Z
Namek is an alien world quite different from Earth, in large part because it has three suns and no moons. A Namekian year also lasts for only 130 days -- less than half of that of a year on Earth. This would create a sense of time far different from what normal humans on Earth would experience, though the aliens on the planet would surely be used to it. Thus, it's possible that Frieza's timetable of five minutes truly did last for that long -- in Namekian time.
As an alien warlord himself, it would be ridiculous for Frieza or even the Namekian people to have a measurement of time that exactly matches up with Earth. This is backed up by the aforementioned cosmological differences between their worlds. In other words, whatever minutes Frieza set his time to were longer than the 60-second intervals on Earth, even if it was only five of them. Lastly, the Z Fighters and their increasingly powerful enemies are constantly shown moving at high speeds, with the more slowed-down action being so that the audience can keep up with them. Thus, it's entirely possible that the nearly 10 episodes of activity, along with Namek's alien cosmology, kept the fight with Goku and Frieza at exactly what the latter said it was -- even if his watch reads a little differently.