This is purely a personal decision. There's no money in registering domains, so you could be losing money if you're making any manual adjustments. If everything is automated, then it likely doesn't hurt anything, and may even move your domain reseller account into the next plan level for more discounts.
I've seen hosts require that if you register your name with them, you must host with them, and some say that they will not host a website if the domain isn't transferred to them too. I personally don't think this should be a requirement.
Many hosts have moved away from the domain registrations and only provide hosting. This is the process that we used internally with design clients (before closing all hosting options and requiring clients to get their own hosting & domains)