A standard commute of 30-60 mins. is when you know where you work, what job you're doing and how long you've been going there.
It doesn't apply to casual relief work unless you have been to the school before and are familiar with routines and things. My line of thought was- if I get a call at 7am, I drop off one of my kids and ask DH to drop the other and try and arrive at the school early. DH travels a lot so I need to drop off both kids when he's unavailable. All this planning is not knowing whether I'll receive a call in the first place.
My reason for being around the '30 mins.' travel mark was so that I arrive at the school by 8-8.15, familiarize myself with the teacher's lesson plans, do necessary photocopying and stuff, etc. and mainly, doing something worth what I'll be paid for.
How bad do I want to teach-I did the one year primary Grad Dip. full time when my kids were 5 and 2. It involved a lot of sacrifices and hard work for e.g. studying in the garage at night because my 2 year old wouldn't leave me alone. Of course studies involve hard work but what I find disappointing is that a lot of us students somehow got the impression that we would be very much in demand and it wouldn't be too hard to find work. It was only in my practicum when the Principal mentioned she had received over a 100 applications for one position that I was shocked.
Some of us have found work and others are doing other things. Try searching on the net for something similar and see the number of responses that come up.