Tomboo,
You should not normally need to put drift lines on a leg of less than 15 nm. As a simple practical matter, on a leg of less than 15 miles you should pretty much be able to see your next turning point before you set off; since you can see the turning point you can very quickly determine and correct the drift by "eye".
Drift lines are useful on long sectors where the end point is too far to see, and therefore you need an interim "how goes it" in order to update your heading. Even so, they are not widely used - you'll get better at map reading with practice, and although they may actually be doing more or less the same adjustments, with better situational awareness most pilots do it without drawing drift lines.
As others have noted, an examiner on a test MAY ask you to demonstrate a drift line technique on a very short sector, but that's only becase he doesn't feel like sitting there while you fly a 100 nm sector!
