I am not sure what you mean by latest Ubuntu. Do you mean the latest stable
9.10 or the latest available, 10.04?

Update is something that you have control over. You can set the update level
based on your own needs. You can turn them off entirely which is not a good
idea or have them upgrade automatically, also not a good idea, IMO. The
default settings advise you of updates and you can decide when or if to
install them.

I prefer to use Synaptic over Update Manager. I like to see what is
happening. Sometimes one upgrade will break another and it will want to
remove a package that I may use all of the time. If that is the case, I will
decline to upgrade the package. Other times I will selectively choose which
ones to install. You can do that from Synaptic better than in Update Manager
in my experience.

If you don't need an upgrade and it is inconvenient or you have reservations
then I suggest that you wait. The one qualification I would make is to do
security updates or you may be vulnerable.

I am not sure what you mean by on the fly. I am familiar with the
expression, but it does not seem to apply given my understanding of the
phrase. All updates are planned by the package maintainers. Executions are
in your control and you have to decide whether to upgrade or not. It seems
not to be on the fly from either perspective.

You do not say why you don't want to to upgrades other than not spending the
day to do half an install. Is it a connection problem? Most of time my
upgrades work in the background and they seldom take anywhere near that. I
just upgrade 352 packages including the kernel and rewriting grub and it
took less time than to type this message on a DSL connection. I was not
inconvenienced in the least.