I have always been cautious about deleting past versions and Autosave of stuff I'm still working on - afraid that I might wind up deleting something common to both versions in question, or various other possible unintended consequences.  However, I'm winding up with what I think is way too many versions, and that can get confusing.  I guess I need "permission" or encouragement (if that's warranted) to go ahead and delete stuff regularly. 
 
Is it a good practice to keep maybe one or two earlier versions, but each time I use an Autosave, or I am happy with my  most recent save - to go ahead and delete everything else?  I'm beginning to wonder if that's what I should have been doing all along, and this is probably a stupid question - obvious, but not to me.  Thanks.

I would do a "save project as" and change the name of the project. Be sure and check the per-project audio folders and also rename  the project path to the same as the "new" name. You should now be able to delete the older (original) project without losing the most resent data. You will lose all of your older takes, but that is kind of the whole point. Before you do this...read up on it a bit and be sure you do it correctly. I lost two projects myself before I learned how to do it the right way. Or just open the new project and make sure it is functioning right before you delete the old.
 
Someone correct me if I'm missing something!

Good and helpful points...and I'm assuming that - having done all that, it would indeed be good to delete the old stuff (my original question) to avoid future confusion and clutter.

Yes. For me this is the best way to do what your asking. I also backup my whole audio folder to my external hard drive every once in a while just for good measure. I get paranoid.

Remember as well that the cwp file is just a pointer to the audio so you don't delete any of that by deleting the cwp.
 
I usually make "landmark" saves. i.e. Save versions such as "tracking finished", "editing finished", "Mix start" etc as the project progresses so if the worst happens I haven't got to go too far back.

<...the cwp file is just a pointer to the audio so you don't delete any of that by deleting the cwp...)  In that case, do the obsolete audio files continue to accumulate after I save new versions?  How do I also safely delete those files?

Yes they will. Use the "Clean audio folder" option under the utilities menu, or save the project as a completely new one in a new folder, making sure the "Copy audio files" option is checked and then delete the original folder.

My system is very much like Karls.
 
Additionally, when the versions I'm saving DO get too numerous, I simply port the whole thing over to 2 external drives and delete them from my working drive.

My first message explains how to do this. You can delete the old audio files after you do a "save as" and change the name of the audio path to the new name.

double post