Well, you can buy a 5 TB external backup SATA III drive for $129.99, which would give you quite a lot of storage space quite cheaply.
 
1 TB drives run from around $50-$75 approximately
2 TB drives run from around $60-$90 approximately
 
Etc.....
 
You could pick up a new drive to meet both your needs and your comfort level, as often as warranted.
 
I happen to approach things this way - with a combination of current drives, internal backup drives or current work, external drives for both active and recently completed work, and more external backup drives for older stuff.  Things that would truly be non-reproducible also have a copy off-site.
 
Evaluate your situation, review the options, and execute the plan.
 
Bob Bone
 

promidi

gswitz
I have 2 GB internal to my PC and 2 GB of backup.

Please tell us you meant TB...

I'm innumerate.
 
Also, as an aside, I have this handy device...
http://www.amazon.com/CoolGear%C2%AE-Drive-Adapter-Universal-Drives/dp/B009VKSNS6/ref=sr_1_13?ie=UTF8&qid=1425261774&sr=8-13&keywords=usb+hard+drive+adapter+kit
Mine was $30 but it basically looks like this one and enables me to plug in laptop hard drives, old hard drives and newer hard drives to a USB port without getting a specific type of drive. In other words, I can use internal drives for storage. As friends discard old PCs, I take them to the recycling place for them and pull out their HDs and stick them on my shelf. I then use them for additional backups or Linux images or whatever.