PARKs can stay as long as parking restrictions allow for and depending on how keen you are it could be hours, so consider the element of time in your PARKs.
PARKs can slowly 'disappear'. In 2006 PARK(ing) in London, Roger Allen and Helena Rivera had 552 rosemary plants that were given away to passersby throughout the day.
PARKs can also slowly "appear". In 2007 PARK(ing) in San Francisco, EDAW slowly changed their space by adding more and more glass bottles.