Having read --JENKINS-11286-- and --JENKINS-20445--, my situation could make use of the following enhancement. 

At present, the Git Plugin (v3.5.1) only allows numeric values to be input on the page.  It is not possible to add a Parameter to the build, say GIT_TIMEOUT_MINUTES and then supply ${GIT_TIMEOUT_MINUTES} as the value on the Additional Behaviours --> Advanced Checkout behaviours --> Timeout (in minutes for checkout operation).  Only a integer literal can be placed on that field.

Now imagine the following use case:

We have a job with 150,000 .wav files, (averaging 10K or less inside) in a git repository that is using Git-LFS.  They change only rarely. The checkout operation is much more time-consuming the first time than once the files are present in the workspace.  10 minutes is not sufficient.  Yet once the files have been pulled down from the git remote, the git operation is much faster, and the default is fine.  

One must CONFIGURE the job to get the longer time and then unconfigure it after the initial load has occurred.

Now further imagine that there are several such jobs, such that you might want to create a Template for handling them, with an initial very high timeout value, then transitioning to the default.  You can only change this setting in the template, possibly affecting other builds.

This could be handled by making Additional Behaviours --> Advanced Checkout behaviours --> Timeout (in minutes for checkout operation) a parameterizable value.