It's an internal combustion engine. Treat it right and it will last a long time. Abuse it and it won't do well at all.
I have one OS .10 nitro engine that is literally 25 years old that has never been rebuilt and runs just fine - granted it only has about 3 1/2 gallonsof fuel through it, but still. On the other hand, I seem to go through weedeaters every couple of years or so - and those are the samebasic engine as in the Baja's.

Honestly though, I think that most people find the gas 2 strokes are more forgiving than a nitro is. Is it worth 2 - 3 times as much? That would be up to you.