The first backup can be done anytime, sooner is better than later. You never know when a drive is about to fail, and it may well give zero warning. That catastrophe happed to me, my boot drive simply died one day, no warning, no issues in advance. It can, and does, happen. So make that first backup! It may take a while as the entire system has to be backed up, but make that first one, you won’t regret it.
How Frequently To Back Up
How frequently to make backups is a question only you can answer. There is no one “right” answer. The factor in the decision of how frequently to backup is, “How much am I willing to lose if my drive fails?” You see, if you back up, let’s say, weekly, and if the drive fails on the day before your scheduled next backup, you lose six days of changes to your system. When you recover the backup, it will be six days old, and the changes since then are gone. Things like email will/should catch up, but pictures/documents/files you have changed in that time are permanently gone.
So, how much are you willing to lose? In the case of a machine being used for a business, losing even an hour may be too much to risk, so you might want to back up every 15 minutes. But consider that as the backup is happening, the system may become less responsive to the user. That loss of responsiveness may or may not be critical to you. Only you can balance the risk of not backing up with the potential loss of productivity as the backup occurs.
On the other hand, if you don’t do much but get email, you might not need a backup but once a week. It’s your risk tolerance that is the driver of the frequency of backups.
When In The Day Should I Back Up?
The timing of backups is another decision that is unique to you and your circumstances. If you are running a business that employees come in at 7 AM and the last one leaves at 10 PM, and your risk tolerance is for about an hour’s work, you might set the backup routine to be every hour between 7 AM and 10 PM, but then no backups during the night because the system isn’t changing. Or if you are running a 24/7 online selling service, you might need backups every 15 minutes every day. But if you are a retired person who uses the system only for email, net surfing and maybe Face Timing, you can let the system make the backups at night, when you are not using the system, just leaving it alone at the end of the day so it can do the backup for you overnight.
I used to be a consultant, working with customers on IT solutions. When I was in that role, I backed up multiple times a day so that my transactions with each customer were kept safe. Basically, when I ended a session and had entered all of the data from that customer, I backed up. That way, very little was at risk. To accomplish this backup, I carried a backup drive with me in my briefcase and did the backup of my laptop while in transit from one customer to the next. It was a pain to do that, but the risk reduction was worth the effort.
Now I’m retired, surfing the net, checking email and occasionally writing an article about computing. My risk is greatly reduced. Now I back up at noon and midnight, using both a cloner and Time Machine with TimeMachineScheduler to multiple drives and locations, plus a sync suite to make an additional copy of my photos. The noon backup is just TM and is quick. The backup only takes a few seconds and works in the background, virtually invisible to me. The midnight backup is with TM and the cloner and goes to multiple locations. It tends to take a few minutes to complete, but I’m not on the system at that time, so I don’t mind the time it takes. This approach meets my needs. It may not meet yours.
So, as you are pondering how often to back up and when to do it, consider your risk tolerance, the potential interruption of the backup to your workflow as it is happening and any other factor like the loss of productivity to determine when and how often to make a backup. But do make one, you won’t regret it.