Also, if Chinese were "in for the long haul," they give the Indian government justification to spend billions on upgrading/building border infrastructure unopposed by the Indian domestic political opposition; and more than this, China ends up incentivizing India to build and grow a domestic military industrial complex to keep costs low (vs. foreign hardware procurements). China wouldn't want this.
Therefore I think they're not in this for the long haul, but to cook instant ramen. They've thrown the world into chaos with WuFlu, and now want to take advantage of the chaos to move up in the world order by doing "superpower-ish" things, so that Xi gets to make his pee stain on Beijing indelible.