If you know what shooting interval you want, you can start to calculate the memory usage.
Let's take 1s shooting interval as an example. This gives 60 frames each minute and 3600 frames an hour. The estimated memory usage per hour is 180 MB = 3600 x 50KB. For a 128GB SD card, you will get ~29 days = 711 hours = 128GB/0.18GB/hr. In order to cover 3 months, you can change the shooting interval to at least 4s or use an SD card with 64 GB or bigger.
If you don’t need to shoot 24 hours a day continuously, you can use Schedule to define the time slot(s) you want to shoot. This will reduce the memory usage significantly.
Note: The maximum number of frames per time lapse video is 15,000 (Default 25fps and 10 minutes playback). If the limit is reached, frames from the existing task will then be saved to another video file. Rather than saving a time lapse video in one big file, you can save it by “Per Time Slot” or “Per Day” using the “Schedule” feature. This offers an easy way to manage and view the recorded time lapse footage.