You could, but then the computer will start complaining that you haven’t backed up in X days, even if it has to the new drive.
You can leave it and always remove it from the list later if you want. Either way you can plug in the drive and browse the files by backup time in Finder when needed.
I didn’t realize Use Both implies that I also have to backup to the old drive from time to time! I thought Use Both means I am keeping the old drive to be available for TM recovery via that “go back in time” Finder interface. Thanks for the tip!
I agree that if you are going to do any appreciable work off a bootable clone, having it on an SSD is going to be a necessity these days. Going back to a spinning hard drive would be torture!
That being said, I am good with a cheap spinning drive for my boot clone. If for some reason I actually had to work for any reasonable length of time off the clone I would most certainly clone it over to an SSD, but if I just want an emergency bootable disk and the ability to restore after getting a machine fixed if the internal SSD did not survive the repair, a spinning drive has me covered.
If all you’re going to do is restore off of it I’m not sure a bootable clone is the right tool. Something like a Time Machine backup would probably be fresher than a bootable clone.
In my case, the bootable clone was the fastest restore option. My 2011 MBP’s GPU died and it would not boot. Noticed this in the morning. I have CCC run a clone operation in the middle of the night. I was able to clone the backup to my wife’s old iMac that we hadn’t repurposed yet. Up and running in an hour or two. A time machine restore would probably take much longer.
I actually have both a clone and a TimeMachine drive hooked up to my iMac Pro. My view is that if I needed to restore the entire system, I would likely do so via the clone, but if I needed to retrieve a smaller subset of files I would turn to TM first.
The clone is updated daily and so it would only be slightly out of date compared to the TM backup, from which I could renew any recent work as well.
In reality, I would probably if faced with this issue build the new machine from scratch taking the opportunity to have an effective nuke and pave. Since all of my data sits on the external Drobo, bringing my data files back online is the easy part of this.
I keep the TM and clones (there’s also a daily clone to my backup Drobo) as well as BackBlaze and Arq, for security against data loss.