Is it safe to rapidly toggle fan speeds?

I'm trying to run a large computation on my Dell Inspiron 620 desktop, making the CPU generate a lot of heat. Unfortunately, the resulting fan noise can be quite frightening, especially at night!

It tus out that this computer has exactly two speeds for the CPU fan - low (~500 RPM), and very loud (~3000 RPM). I've been playing with fancontrol trying to make the fan noise more bearable. I wrote this bash one-liner to work around this limitation:

while true; do echo 191 > /sys/class/hwmon/hwmon1/pwm1; sleep 0.35; echo 192 > /sys/class/hwmon/hwmon1/pwm1; sleep 0.36; done

Running this script seems to make the fan spin at an appropriate speed. Is it safe to run this script for extended periods of time, switching the PWM value between "slow" and "fast" 3 times per second? Will it wear out the fan motor or other components? Are there other, less hacky ways to make the fan run at a speed that sufficiently cools the CPU without waking me up at night?

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