I would suggest as an alternative Stretch audio to a specified length then you won’t have to keep changing the length control in the effect. It’s a Nyquist plug-in - see Download Nyquist Plug-ins - install for how to install it. It does change the pitch as well as length, though, which you may not want.
You can also use that Stretch plug-in in a Chain (see Doug’s link).
Gale