Details of Propagation

[Whizkid25468]

Just a few quick questions from a newbie:

When are the root servers (supposed to be) updated? I keep hearing 5am/pm
EST, but each one is accompanied by at least one 'I'm not sure'.

What's actually involved in registering a domain name, between the point the
registrar approves and the point where the root servers get told to add the
appropriate delegation records in the next update? I've read a few things
suggestive of seperate delays, to do with notifying various organizations or
something, but nothing particularly ... understandable.

Are there differences in delays between changing a domain name's name
servers, registering a new domain name, and registering a new name server,
and if so *why*?
My name servers took three days to get their glue records after
registration, but when I change a domain name's nameservers, the root
servers usually catch on shortly after the com zone's SOA serial#
increments. There's obviously a difference, but I don't know exactly what it
is.

Finally, I've been *unreliably* informed that propagation time from the
point of view of using your ISP's nameserver can depend on the size of your
ISP, the type of nameserver you're on, and how often it's *set to update*.
Isn't propagation (once the root servers update) purely dependant on the
TTLs of the affected records? The size of the ISP shouldn't matter!

Sorry if these've been asked before, but I've been looking for a couple of
days, and can't find anything concrete, and I haven't found the answers in
previous posts in here either. Desperation slowly growing.
I realise that these aren't exactly questions on BIND, but if it wasn't for
discovering BIND and installing it, I wouldn't have these questions, and the
lack of answers woudn't be annoying me right now. And this looks like a good
place to find people who know what they are talking about.

Thanks In Advance
Whizkid
/:-)<<