After spending 20 years in the IT field I can tell you with absolute certainty that computers don’t always give good indications when a drive will fail. Things happen – you have to take the time to make sure you’re protected in case they happen to you.
What if you download those portraits to your system at the end of the day and the next morning the system won’t start, or the files are corrupted.
First of all your disks should be backed up every day. If a drive fails, or someone accidentally deletes or over-rights a folder structure this is the best way to make sure you can quickly get back the missing files.
Making a backup copy of the master files for the client/project onto DVD and then storing those in another location is also something every professional should consider. While your clients might sympathize with your about the fire that destroyed you’re computer system if the only copies of their wedding photos where on that system you better make sure your insurance is up to date because you are likely to be sued.
This advice is just as important to the amateur photographer as well. Make a backup. Now make a second backup and store it elsewhere.
The same risks apply to the amateur except that it’s their families memories that could be lost forever due to fire or theft.
If the DVD’s are a bother to you for your home files consider a professional account (even if you’re a home user these are cheap enough) on a site like Flickr, Smugmug or Zenfolio. Upload large versions of your files there. It’s cheap off site storage and disaster recovery.
Remember these memories you’re capturing either for yourself or a client are meant to last a lifetime, not just until your next computer disaster.