This greatly depends on how old your Jeep is, how often you drive it, and how much off-roading you do. On average, you should top the coolant off every 25-30K miles. Again, older cars might be “hungrier” and consume all that liquid in 20, or even 15K miles (newer rides, in turn, require refills less often). So, just remember to keep your eye on the coolant level and to refresh it whenever the level drops below the marked line.
This is important: make sure you completely drain the old antifreeze before adding the new one. Trust me: you don’t want any residue to get mixed with the fresh coolant, as that could lead to engine overheating.