I don't think Photoshop has ever crashed on me. 3dsmax crashes are rare, but I have 5 autoback files saved at 3 minute intervals, means I hardly ever lose anything even if the whole computer decides to shut down for no reason.
incrament saving + autobak every 10 minutes with 8 bak files. plus ctr+s often enough. While photoshop is kinda reliable, 3dsmax is terrbily buggy sometimes. Especially when it comes to import obj files from zbrush. Argh. Downtimes and crashes....
I save a new version every time I do something I think is worth keeping. I have over a hundred iterations of the model I'm working on right now. So I guess my answer would be no, I don't ctrl-s. Frank the Avenger
I usually save every 10-15min, and each time I do, I'll check the file into the server. At home, I have 2 external 120GB drives, so I make multiple versions of each file. When the file is finalized, I'll go back and delete the 'working' files, and keep the final.