FB, not picking on you, but:

I'm posting this response only because I believe this popular myth should be dispelled. People often post this, and it's largely untrue - in 90% of the cases this is simply not practical or economically sensible.

First, most "welders" are welders and have no experience brazing, or are not highly skilled at welding on material as thin as bike frame tubing. Most welders would probably ruin your frame if they attempted a repair. If the frame was still usable after the repair, it would probably look like crap.

Qualified frame builders usually have a bunch of new frames to work on, they're gonna be reluctant to drop their jobs and fix your (probably, relatively speaking) cheap frame.

Even if you can locate a qualified, willing repairman, he's unlikely to be near where you breakdown. So, strip the frame, ship, frame is repaired, ship back, rebuild. Thats a lot of time and money. The frame repair alone would cost $150-$300 bucks. Then there's the eventual paint or powdercoat job you'd want (unless you LIKE large contrasting panels of gray or red primer) - another $XXX .

So, its probably more sensible (and usually the only option) to replace a damaged frame. Certainly something like a cheap LHT. Or any other steel frame on a bike that sells for under $1500 msrp.

The whole "steel frames are field repairable" is basically a myth (it may have been true 30 years ago, in europe). If you tour and breakdown in Taiwan and speak Mandarin, then a steel frame may be advantageous.

I bet if you conducted a survey today, you'd find as many welders skilled at TIGing aluminum as those skilled at TIGing or brazing steel.

Otherwise, pick a frame based on fit, cost, and reputation of maker/seller. All common frame materials can be suitable for touring if the frame is designed and built with the rigors of touring carefully considered.

To the OP: aluminum can certainly work in frames for heavy duty use. Cannondale staying in business so long is simple testament to this fact. Its more likely that your finite interest in bicycling will be exhausted before the number of fatigue cycles required to break your frame have accumulated.