Professional timelapse workflows can get complicated fast, when it comes to setup, capture and post-production assembly. There are many considerations to make when it comes to interval math, digital memory considerations, exposure changes, framing for elements that don't exist yet, to keeping the capture camera rig safe, powered, able to monitor, and clear from foot traffic so no one bumps the rig or blocks the view.
These are just some basic considerations to make for timelapse creation in which there is typically a manned camera rig or daily setup/checks and control of the camera on site. Let's consider this as a regular or 'short term' time-lapse. Typically these are subjects in which the capture ranges anywhere from an hour to a few weeks.
Long-Term timelapse complicates the above process yet again. Take the basic workflow and considerations to be made from the above process then add in the further considerations that come into play when we're dealing with long periods of time.
These are considerations such as lighting changes, weather changes, operating temperatures, theft, mounting the rig, long-term power considerations, memory and storage calculations, more complicated interval math, capture scheduling, and of course perhaps most importantly is automatic backup of captured frames and being able to monitor the on-going capture process off site to make sure everything is running smoothly.