It isn't only a matter of the refund. Would you not agree that a three-year period would be useful for someone who guarantees a loan? If, for example, the loan falls through and the contribution has to be repaid over 3 years, then it would be more logical to say that the length is 3 years rather than 18 months.
Also, I would stipulate three years rather than let the whole thing drop. That is because a government mandate usually lasts three or four years. If an association or a candidate has not finished paying off the loan after three years, then, one way or another, there could be problems for the next campaign.
This is not like a regular financial market transaction, because we must all deal with a short electoral cycle. It would be in everyone's interest to limit the transaction to no more than three years, and I think that a three-year period is reasonable.
