from the gov immi web site:
'Planned system maintenance
Every Wednesday from 5 am to 7 am AEDT (GMT +11).
The following systems may become unavailable during the above times:
•eLodgement (Online Applications and Citizenship)
•Visa Entitlement Verification Online (VEVO)
If you receive a 'Server 500' error message during this time, you are encouraged to try again after 7 am AEDT (GMT +11).
We apologise for any inconvenience this may cause"
yes, dont wait until the last minute to apply for visas.
and not all evisitors are approved instantaneously. there is still a chance that your application will require additional info/perusal before approval. we have instances here of that process taking up to 4 weeks.