But for the price, a set of chinese carbons is worth considering, not just for the width factor, but also for the stiffness and the fact you'll barely need to touch them after the initial break in period.
Maintenance (or lack therof) post initial break in (or even build) is a function of how well the wheels were built in the first place, not what rim (or otherwise) material was used.
My AC Wide lightnings (29) and DT XR 1450 (26) wheels have required zero maintenance post build let alone after "initial break in".
As for carbon versus Al for rims, both have pro's and con's so factor best fitness for purpose in decision.
"Aluminum and carbon fiber are good rim choices. I like aluminum for mountain bike applications because aluminum is “ductile,” meaning it will bend without breaking. This is great for MTB because you hit things when you ride and sometimes you hit things very hard that can cause rim damage. Aluminum is forgiving and it is better priced for riders to replace them when they have a mishap."
http://www.pinkbike.com/news/To-the-Point-Bill-Shook-on-Wheel-Building-and-Wide-Rims.html
" They (AC Wide Lightnings) were designed as an XC rim that would ‘plump up’ a smaller tire to have more volume, allowing for a racer to get ‘more’ tire for less weight, but they are good even on a trail bike as long as you keep it within reason. But if you are in a situation where rocks and hard rim strikes on the rim wall and the bead area are a real certainty, then the Wide Lightning might begin to show some dings and such. So if we were looking for a wide rim that is still light enough to be fun and yet be very tough for impacts and overall wheel stiffness, then stepping up to the American Classic Carbonator might be just the ticket. According to Bill Shook at AC, the American Classic Carbonator carbon rim was intended for something like Enduro or more aggressive trail riding."
http://twentynineinches.com/2015/09/21/american-classic-carbonator-29-out-of-the-box/