Through experimentation, I've found that the Prism will access and write to a 64 Gb microSD. Of course the use process is somewhat unstable, but it can be done. That said, please allow larger microSD's, up to 128 Gb to be used properly (instead of "hacking").
While the internal battery has an effective run time of about 30 minutes, using an external battery, I've been able to do time lapse photography for over 4 continuous hours.
I understand that 64 or 128 Gb seems excessive, but during trips in the Alps, friends with GoPros were constantly changing 32 Gb microSD's as well batteries. My 50,000 mHr (yes, fifty thousand) battery will keep the camera running non-stop for a day. Having a microSD large enough to handle a day's video allows editing the day's riding down to usable short videos. Otherwise, the beginning or end of a riding sequence may be lost.