Does "f 0 z" work?

Quoting David Worrall <david.worrall@iis.fraunhofer.de>:
>
> In any event I was trying to avoid f 0 36000 if possible ? as I want  
> to it to run weeks, not hours?
> do you know how large the "36000" argument can be?
>
> Perhaps I can send the  'f 0 command multiple times?
>