well, ipv6 defines periodic router-advertisement messages that results in ipv6-hosts recomputing currently active parameters e.g. mtu, lifetime for link-prefixes etc. in the worst case, say when the ue is idle, this might result in paging, which in turn causes establishment of radio-bearers, moving ue from idle to active state etc. etc. which most definitely cannot be good for battery life.

also, the claim about "With a static address, it's easier to keep a data session alive while a smartphone or tablet travels with the user from one cell to another" is slightly disingenuous. typically address allocation in cellular networks is via an end node like ggsn or the pgw (lte). cell-to-cell movement doesn't constitute a "rat" (radio-access-tech) change. only when you move from lte coverage area to say a cdma area, handover procedures kick in, and then too, for session continuity reasons, end-node-address doesn't change...