Clean up
Monsieur - I use CCleaner (free version) regularly. First time you run it you will be amazed at the space saved (temp files etc.) You can choose to keep Internet history or not/cookies or not etc.
As Ianf says, bigger drives dying loses you more data; they are quite cheap so get a spare that is backed up less often. How long they last is a "piece of string" question, but they do die eventually (1-10-100-1000 months?)
You could consider putting a larger disk in the PC itself (I'm up to 500GB and that is filling up!) but I am considering a signing up to a cloud service or setting up FTP online with my network disk (dual RAID) although if thieves take that I'm stuffed (my old house was burgled this week, so was a friend's - UK must be in desperate times as both were occupied at the time).
Most of most peoples data are photos and music; I guess once they are off the PC I will be good for years with the 500GB.
My 2c (as we say down here)
A