Speaking purely for myself, as I noted above, I've had good success with a "sharpening" focus. My weekly 15,000 training yards is approximately 20 to 30 percent of what an elite swimmer does.
This doesn't leave much room to drop yardage, especially considering that I typically swim the longest events at Masters Nationals. So I keep my yardage relatively consistent until just a few days prior to an important meet, then reduce it more steeply over the last two to four days.
The more significant change is in using shorter repeats and shorter sets in my "race rehearsal" swims. My main focus on such sets is to tune up my nervous system by swimming as close as possible to the speed, stroke length and stroke rate I'd like to maintain during the race.
During these sets I visualize highly specific signals from my brain innervating my muscles at the precise loading patterns they'll experience during the race. My goal is to make it inevitable that my neuromuscular system will work as I desire.
But I have to be careful to do these repeats without creating residual fatigue. Within the last five to 10 days prior to the meet, I need to be able recover from any work of this type quickly.
Here's an example of such a set: In May 2006, at Masters Nationals I hoped to swim under 20 minutes for 1,650 yards, a pace of about 1:12 per 100. Five days prior to the meet, I attempted a set of 8 ? 100 on 1:30, trying to hold 1:12 at an 80 percent effort level at 14 to 15 strokes per length (SPL).
I couldn't do it; it felt too hard. So I tried repeating 75s on 1:10, holding 54 seconds. I could do this, but it still felt a bit too taxing, so I ended up doing a series alternating a 50 and a 75 at 36 and 54 seconds respectively, at 14 SPL.
After a few rounds of this, it began to feel easier so I added a 100 to the mix. Each round consisted of a 50, 75 and 100 at pace, plus a 25 easy between rounds. I did four rounds like that, feeling exactly the way I wanted.
Five days later I swam 19:52 for the 1,650 while holding a 1:12-per-100-yards pace throughout, placing third in the 55 to 59 age group.
What's the lesson? Taper should be individualized. Use it to rehearse the exact stroking pattern (stroke length, stroke rate and volume) you hope to maintain in the race, while also focusing on making that pattern feel as relaxed and sustainable as possible. For my shortest races (200 Fly, 200 Back and 200 Breast) I may do several rounds of, say, 2 x 25 plus 1 x 50 with ample rest and some extra recovery swimming to get the same non-fatiguing-rehearsal effect.