I use silica wicks. I rewick them when enough sediment collects on them that it impairs the wicking/heating/vaporizing/taste. Where that point is is largely a judgment call, but eventually I perceive the performance has dropped. I do not dry-burn and prefer to use fresh wicks.
I could probably extend wick life by paying closer attention, catching the build up a little earlier and doing a little dry burning, but I'm okay with how I do it.