Generally speaking… If you use the laser at half power, will it last twice as long?
The laser is a LOT like a lightbulb. Lifetime is a matter of probability, not precision. So just being in use at all is causing some wear, and can at some point happen to kill the tube. Precisely why the tube finally breaks (and where) will likely boil down to essentially a manufacturing defect. Not to say it was poorly made, but rather to say that structurally… some point is the weakest point in that particular system, and that is where you will fail.
Higher power will mean more stress, but not in a particularly linear fashion. And the power you run the laser at in any given moment is the exact power you need. You cannot just run at half power and still cut through or engrave the same material. You COULD run at half power for twice as long and cut or engrave the same thing, likely with some change in staining/marking from smoke generation.
But overall… the only change in usage pattern which will influence laser lifespan is not using it at all.