It’s nice to see the words ‘stroke rate’ used when referring to speed. Sometimes we get too preoccupied with lowering our stroke count and go beyond our optimal; in other words, a balance between using a suitable number of strokes and maintaining speed.
I’d only look at increasing stroke rate if all traces of drag had been eliminated from your kick and your ‘catch and rotation’ were effective. (These are key ways to improve the length of your stroke.) Increasing turnover before this just increases the amount of times you create drag within a length.
An advanced swim ‘golf concept’ I’ve developed will help not just work on an optimum rate but also put it under some pressure, so you can see when it breaks down and measure progress. Start sensibly, with an interval where you get at least 15secs rest. For example:
12 x 25m off 40secs. This means you swim one length in 25secs with 15secs recovery. An aim for a strong swimmer could be 25secs and 22 strokes over 25m; in other words, a golf score of (25 + 22) 47 or under on each length.
Repeat for 8 x 25m off 35secs, adding 25m recovery before attempting 4 x 25m off 30secs.
As your technique improves, you’ll be able to hold a lower stroke count off the same intervals. As fitness improves you could start the set off 35 and reduce to 25secs. Lowering your golf score shows improved all-round swim progress.