China has been building freeways at a fever pitch over the last decade or two. It is well known that China loves to build things as cheaply as possible. I remember reading about a bridge that was partially built of styrofoam. What's going to happen in, say, 25 years when all these cheaply built highways start falling apart? Will they just patch them up or will they simply fall into disrepair?
That assumes all infrastructure in China is built on the cheap, with substandard quality, and will fall apart within 25 years. I doubt if that is the case. Most collapses are either due to illegal overloading (coal or sand trucks that weigh over 200,000 lbs) or local projects mucked up.
Note that a lot of infrastructure in the western world was supposed to last 100 years, but are now in need of replacement decades before the estimated service life. Many bridges built in the 1950s and 1960s have a poor rating, whether that is in the United States or Germany.
I'd be more worried about the financial sustainability of many expressways. Many provinces are indebted significantly due to the amount of expressways constructed in a short period of time, without sufficient toll revenue to pay back the investment. Most of these expressways need a long ramp-up period, especially in more rural areas.
AFAIK Shanghai S5 (Hujia expressway), the very first Chinese expressway, has been there for 25 years now and is still standing. They even removed tolls from that road a couple years ago. Another 'old' expressway is the Beijing-Shijiazhuang section of the G4 Jinggang'ao expressway, but they are rebuilding it into a 2x4 superhighway, as they are doing with many backbone expressways now. I think in 25 years from now the Chinese construction sector will collapse due to all expressways already built.