To expand on the matter:
1. What happens with no maintenance?
Answer: Reduced cooling performance over time. Dust on the convector and possible problems with stuff getting stuck inside the cooling block(s).
Leakage is typically not something that occur in a static loop.
2. How often does it need maintenance?
Dusting your convector could be done frequently. Depends on how fast dust builds up there in your usage.
Taking the loop apart to clean it inside is a matter of manufacturer's recommendations, the cooling medium used and your general cooling performance.
If you see algae or residue in the tubings you definitely need to clean the system.