I once started focusing on getting my Strokes Per Length (SPL) down as far as possible. I once did 7 strokes many times for 25y. But it was a very, very slow 25y. As I tried to up my speed and stroke rate, I lost the 7 strokes almost immediately. I asked Coach Shinji about this, and he told me that while low SPL is a great goal, it’s probably not something to obsess about at least not in that way.
He then told me that constructing a tempo vs. SPL matrix on a spreadsheet would be a better idea. You establish baseline SPLs at a given stroke rate using the tempo trainer, and then that would set goals for you to try to beat at each tempo. Speed would then come naturally, or else how would you do a length with one less stroke at a given tempo?
Earlier last year, mine looked like (tempo in seconds, SPL for 25y):

If you’ve ever swam at >2.0s tempo, you’ll know that this is quite painful to keep balance but a great practice to show that you have awesome balance in the water.
Each swimmer will have some sort of SPL that is dependent on their swimming skill and body type/shape. Achieving the 4-5 strokes that Michael Phelps reportedly does for 25y probably isn’t possible for guys who aren’t as tall, or as skilled, as he is!
When I practice at these tempos and compare the SPL results to my matrix, I sometimes see efficiency drops. This can happen between days, and between changes in focal points and technique practice, especially if I’m tired or extra tight, or my concentration for some reason isn’t as good on some days as others. When my efficiency drops, I usually go back to drilling basics with single focal points and then move back to whole stroke to see if my efficiency comes back. If not, I may just get out of the pool or else I risk imprinting bad habits.
More matrix notes:
1. Establish your base SPLs and their tempos and record them.
2. You can record more granular tempos if you like but I think the .1 and .05 steps provide enough granularity for this exercise, even as .01 steps can have positive effects on neuromuscular adaptation to higher tempos.
It’s just that who has time during a workout to go through all ranges of tempos at .01 steps? But of course you can focus only on a narrow range during any workout and just record that, even at .01 sec tempo increments.
3. Notice where your SPL jumps by 1 or 2 when go down .05/.1 seconds. This is evidence that your form is breaking down. This is also a great tempo point to drill at and around further because you need to get your form better.
4. Record each time you can remember to, your tempos and times. Also record your mental/physical condition. Try to find patterns over time on your physical and mental condition as it affects your swimming.
5. The ultimate goal is to know how fast you’re swimming instinctively due to your swim tempo and to develop gears in which you can shift to, in order to cruise, to rest a bit, to accelerate past others, or to up the effort during the latter part of a race when others are tiring and getting slower.
Terry Laughlin talks about winning races by being able to maintaining speed over long race distances. Remember, Terry isn’t necessarily the fastest on sprints but he can maintain high cruising speed over the length of a race when others start to falter on form due to fatigue!