I thought time was cyclical
You remember hitchhikers guide? Remember the resturaunt at the end of the universe? Its like that. This is a self contained contiuum. It is only found in a particular part of our time line for no matter how long it exists. You have to ttavel back in time to access it. Or forward I suppose but how would you know its there? Once its reached its apex similar to when the resteraunt has seen the big collapse, or what not, it travels back to the begining again to live again over the same time. And of course some is lost in that time but not everything and things can grow more than you would expect them to. But because each time they go back and "relive" the past is unique in a sense timetravellers wouldn't risk seeming too plentiful in fact I'm not sure you could go back to any other loop than the one currently going during yourt time line. Because no matter how many people go back there is an infinite amount of space and time to accommodate them.