When I replaced my upper bushings to fix a similar squeek, I didn't see,
hear, or feel anything to indicate that the problem had a deadline related
to safety or even functionality.  If you don't mind the squeek, I think
you can leave it alone.  If you drive fast, the wind noise masks it.

Incidentally, I have not had any apparent problem arising from my failure
to tack weld the new bushings into the control arm.  Knock wood.
B.
Wm Kennedy
kennedy@admin.njit.edu