Raspivid -t variable not timing out

I'm really not sure where to ask this question.
I've set up two bird boxes each with a pi zero w with ir camera in them.
When I start the cameras streaming with raspivid streaming to youtube they are sending the signal nicely but I want the stream to only last about 30 minutes at a time. I've looked at the documentation which says that you use the -t variable to set the length of the capture in milliseconds. I've done this but the stream does not stop!
What I really want to do is set the command as a bash script which is called by cron each hour to stream for half an hour with each pi alternating so it doesn't kill my bandwidth too much! Any thoughts or help appreciated!
I'll then start on my "why does the cron job work on one pi and not the other" question!
Code as below:

raspivid -t 180000 -o - -w 1080 -h 720 -fps 25 -b 4000000 -g 50

The code then pipes to ffmpeg but that bit works fine!

Edited to add:
I know that 180000ms would be 3 minutes not 30 minutes but it doesn't even do just 3 minutes it won't blooming stop!

My suggestions would be to remove all the other options for now and just use the -t and the -o option.

Yes I realize that they should have nothing to do with this problem, but just get them out of the way and use the defaults for the time being.

Instead of 3 minutes, try 3 seconds so that you can try it iteratively.

Recommend you try putting the output to an actual file versus stdout and see if this continual problem has to do with the redirection to stdout over a file. It may be an inconvenient feature/problem that isn't documented. Unsure, I can't test that one myself. I used to use a Pi to capture still frames, but it was still frames only and I used a different application but it worked great.

Dumb other things to try, if the capture does stop when you put it to a file, try putting the -o - either at the beginning or the end of the command string.

If you find any success with capturing to a file, I wonder if instead of -o - you could use -o /dev/stdout.

For that matter, what happens if you never give it a -o argument? Could you just leave that out and pipe it to ffmpeg that way?

I'll try that and report back.

Ok, so the timeout works when the output is a file but not when it is sent to ffmpeg. with the -o - variable.
I'll try the /dev/stdout option tomorrow, time for bed here!
Thank you for your help so far.