linux - Kill process after it's been allowed to run for some time

I want to limit the time a grep process command is allowed to run or be alive.

For example. I want to perform the following:

grep -qsRw -m1 "parameter" /var

But before running the grep command I want to limit how long the grep process is to live, say no longer than 30 seconds.

How do I do this?

And if it can, how do I return or reset to have no time limit afterwards.