Why does Time Machine take so much time to backup my files?

Kelly Tuesday wrote:

If I wait a week to back up my files, but the only new items are a few pdfs and a few very small numbers and pages files, should it take over an hour to back up my 500 GB SSD MacBook Air? I've gone thru each potential problem item in the Apple Support article and verified my disk, but none of them apply. I have two backup disks kept at 2 different locations. Each one has the issue. Thanks in advance for any ideas.

If a Time Machine backup takes longer than you expect

https://support.apple.com/en-us/HT204412

Time Machine does consolidations by week and month, and it will backup anything that has changed in your home directory, and the operating system too. So you are encountering the customary preparing to backup delay as it hunts for the files that are backup candidates, the actual daily backup, and then it will do its weekly consolidation on top of that. I will be slow.

Your Time Machine backups will not take as long if you increase the backup interval to at least daily, so say nothing of better backup protection than weekly granularity.

My iMac is on from early morning until around 10:30 pm. Time Machine runs approximately every hour that the iMac is on, and to a USB3 connected 1TB SSD (because I have a 250GB internal SSD). Most of the time, I am simply unaware of Time Machine running as it happens too fast to notice. With my MacBook Air, if not being used on a table, where the Time Machine drive is connected during its usage, it is purposely backed up at first opportunity when I get home that day.