Exit Permit Only (EPO) is not the same as MERP. You have to apply for EPO at immigration to officially end your KITAP. They will take your card, stamp your passport with an EPO, and it will say something like "Must leave Indonesia within 7 days". Only then is your KITAP officially terminated.
If you are abroad, and will not be in Indonesia before your MERP/KITAP expires, you should contact the Indonesian consulate in your area and let them know you are cancelling your KITAP.
Simply ignoring it and letting it expire is not recommended, as it may complicate later applications.