^ But don't you also mean, if you edge (nearly) weekly? It also depends on the soil height relative to the concrete height.
In some soil it can depend on the performance of the string trimmer, but in my clay rich soil, using a commercial string trimmer that runs like a scalded dog, it's not penetrating the ground much at all, just uses up a spool of trimmer line in nothing flat to get not much done.
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I may not be trying hard enough... I don't want to edge. It's not the labor (well it's that too) but rather the senselessness of it* Different types of lawn grasses might have different needs, as well as the land owner caring how perfectly it's edged. When I mow over an edge area, if the grass is too tall, it gets sucked up and cut off and I don't care if the short remainder leans towards the pavement. Just sayin'...