In the past 11 years, I've owned two Echo trimmers. I bought a GT-200R used about 10 years ago. I ran it until last summer. Great little curved shaft trimmer. Last year, I bought a PE-250 edger to complement the trimmer. The edger got stolen about a month later while I was on a job.
So I replaced both with a new PAS-225 last summer. I have the edger attachment and the straight shaft trimmer attachment. I expect a long service life from it. I just sold the GT-200R a few weekends ago for 50 bucks, still running like it did when it was new. I started running Trufuel in it for the last few seasons. I think it burns much cleaner than the fuel I mixed.
I set the idle on my 2-strokes about as low as they'll go and still run smooth. They just putter along, quiet as can be. I sneak enough throttle to get the trimmer or edger head spinning without bogging. The edger takes more throttle, especially when cutting through thicker growth, probably 75% or so. The trimmer can get by on just a crack of the throttle (maybe 25%). I do rev it frequently while walking across the lawn, to keep it "cleaned out", but I've never had any issues operating it like this.
Because of my excellent experience with Echo, I bought a handheld leaf blower (ES-250) late last season. That's been real nice; first time I've owned one, and I use it often. It's got the shred-and-vac attachment that lets me suck up leaves and bag. It's useful for sucking leaves out of mulch beds and the like.
So that's my story. I've never had a handheld piece of equipment to actually wear out. Lifespan on a quality piece of equipment like an Echo or a Stihl should be as long as you care to own it. A bad piece of equipment is probably bad luck. A string of dead equipment may be something else at play.