I used to be a professional brushcutter/tree removal contractor. Experience taught me (early on) that even for occasional use, a professional two-stroke power tool by Echo, Tanaka, RedMax, Robin, Husqvarna, Efco (Italy), or Stihl is by far the best value. I have an Echo SRM-2100 that I've used since 1998 and that has at least 650 hours on it (I stopped keeping track when I left the business). The box-store trimmers really are terrible, and they get terrible reviews because of it. The pro machines are more expensive, but will last so much longer that you will save money, probably after the first season when the box-store trimmer would require replacement. And you will be able to get parts and service for a quality machine if and when you need them.
If you must have a gasoline-only four-stroke, then Honda and Robin (Makita) are your only choices. Shindaiwa, Stihl, and RedMax make miniature four-strokes, but they still require 50:1 gas-oil mix. The Honda and the Robin are the only mini four-stroke engines that have a separate oil sump and will run on straight gasoline. And they are EXCELLENT machines, only expensive and somewhat heavy. But they will last you a lifetime, don't doubt that for a minute.
Remember that any new trimmer you choose, whether it's a $59 WeedEater or a $250 Echo, will be set lean from the factory for emissions compliance purposes and will need to be richened up for long life.
Gasoline-powered equipment is not like hand tools, where the occasional user can get by just fine with Craftsman or Stanley, and Snap-On and Proto are only really necessary for daily users. A string trimmer doesn't care who is at the throttle, homeowner or professional landscaper. The cheap ones are designed to last for only a short time, which is really wasteful.
Of course, the number one thing that kills small engines (regardless of the manufacturer) is old gas, or allowing gas to sit in the carburetor. Even the crappiest engines would last significantly longer if they weren't allowed to sit with gas in them over the winter.
And, last but not least, don't forget your PPE when using a string trimmer - earplugs, long pants, and safety glasses. I once had a rock thrown at my safety glasses that otherwise would have sent me to the hospital for eye surgery.
Have fun with it, whatever you choose!