Good point... lets say 7 years on, burst pipe, lose all the coolant.... waste of money..
however, it is very rare to lose ALL the coolant in one go.. you should be checking your coolant level regularly, and should be able to spot a leak, and have it repaired without losing it all..
but yes, still a good point..
All you need to know is you should only use Red or Pink coolant, as it doesn't mix with green or other types.
John