As someone who has spent far too much time dealing with the Domain Name System, I get kind of miffed when people insist on creating names that conflict with the DNS ordering. You see the DNS naming works from right-to-left (the wrong way around if you’re reading this in English).
Take the name for this site – really.zonky.org – which is admittedly a rather quirky name. The most significant part of the name is at the right (org – and yes I’m ignoring the really significant and invisible “dot”). The next most significant part (zonky) specifies what organisation has registered the site (me), and the least significant part (really) points to one service at that organisation.
So when people ask for names that break that ordering it is ever so slightly irritating – for example if you have a service called mail.zonky.org and wanted a test service you might request mail-test.zonky.org which breaks the ordering of things. As an alternative, test.mail.zonky.org doesn’t break the naming, looks a bit nicer, and ultimately more reasonably flexible.
Let us look at a slightly more complex example; let’s assume that we have a domain called db.zonky.org and want to register a service name for each database. We could register names such as db-addresses.zonky.org, and db-orders.zonky.org, or we could register them instead as addresses.db.zonky.org and orders.db.zonky.org. In the later case, I can very quickly write a firewall rule that allows access to *.db.zonky.org (whereas db-*.zonky.org would not work).
Ultimately suggest names in DNS naming order unless you can justify why it is not suitable.