It's made of metal - proper metal that I can weld up if anything should need it. No alu frame or radiators to fail and it still goes like mad. Can't see any of the latest *&%$ hot enduro bikes still running in 20 years time!
But have you been on a XR650R and would it be worth the extra, in this case. $500.00 to $1000.00 dollars that it cost me to get the 2000 BPR. Everyone that had owned or been on both bikes said go with the 650. The aluminum isn't an issue as I can TIG weld that with no problem. But I did liked the idea of not having to worry about a liquid cooling system on the 600. But in the end the better suspension of the 650 over the 600 is what made the decision easy for me. As far as still running in twenty years, that isn't really an issue either as I'm sure I will have long since moved on to other bikes. Then again in twenty years I'll probably not be riding dirt bikes as that would put me in my 60's. But who knows?