Not sure what you mean by clean up. Time Machine does it's thing and then hibernates until it's time to do next backup. I do not interupt it.If you allowed Time Machine to do its own clean up, you should have a folder for each month, if not weekly. Select a folder with an older date then go to HD > System > Library > Receipts. You can check for com.apple.pkg.update.os.
Depending on the update you can identify it by the title...i.e. Combo.10.xx.xxx
Recent installs do have a receipts folder but older one's don't. I know that one of my folders OS was Mountain Lion but the folder "receipts" doesn't appear in the list. would this have been organized differently in earlier versions?Not sure what you mean by clean up. Time Machine does it's thing and then hibernates until it's time to do next backup. I do not interupt it.
I drilled down through HD / 2016-02-27-211737 / Halifax2015 / System / Library / ...
I have 73 folders but none are labeled Receipts
thanksThinking back, you could be correct. My back up does not go that far. - I don't keep more than 2 years on my Time Machine.
When you let Time Machine do its thing, it does its own monthly clean up deleting the hourly, daily backups and keeping the weekly.
Depending on how you downloaded and saved the updates and OS installer, you can check the downloads folder. There were some OS downloads that went directly to the Applications folder. If you saved the download, you can find it in either one of those folders in your Time Machine backups. The downloads folder would be in Users>your user name folder.