I've become anal about backing up my computer over the last few years. When I was working at a corporate, I didn't worry about it; it was IT's job to back everyone's files up on the server each night. When I started my own business nearly ten years ago, I backed up periodically onto CDs. Then I bought a portable hard drive. The night I bought it I plugged it into the laptop I had at the time and backed up all my digital images. There were many that I hadn't backed up onto CDs at that point. Because those were the days of USB 1.0 it took ages to back them up, so I decided to leave my work files, which I hadn't backed up recently either, for another day.
Guess what? Yep, the PC crashed that very night, soon after I'd completed the photo backup. It crashed in a major way, too. The hard drive was scratched, I learned from the repair man. Weeks and hundreds of dollars later I got the machine back with the files recovered. It had cost me dearly in more ways than money, as I had to redo a LOT of work in the six weeks it took to recover my files.
Since I've had my Mac I've used Time Machine, which backs up every hour. It's a brilliant system, as I found out this week.
Last week my Mac crashed. The logic board and hard drive had to be replaced, and I didn't have my Mac for ten days. I used a borrowed older Mac and my old Windows PC to cobble together enough software to keep on top of at least some of my work during that time. I had the pleasant sensation of knowing Time Machine had done its job; I could access my external hard drive and get into the backups to retrieve files and keep working.
When my Mac came back it had a new and very empty hard drive. One click of the button in Time Machine and all my files, including software, were loaded onto the new drive. Everything worked. I had a hiccup or two getting the Adobe products I have to recognise their licences but a call to Adobe's excellent support team fixed that.
I can't stress to everyone enough the vital need to keep your backups up to date. You never know when you'll need them.