Best Practice for Bulk Silo Traceability

My company is working on implementing an ERP system which will also have lot tracking and traceability features and I am trying to determine what the best practice would be for traceability in bulk silos and bins with comingled lots that do not unload evenly and was wondering if anyone could offer suggestions. 

1. Track all lots until the bin is emptied, which could occur every two months or more.

2. Use the last x (perhaps 10) lots. When the 11th comes in, the first of the 10 drops off and that cycle continues.

3. Time based. After X days/months/etc a lot would drop off. For instance, in a tank or silo that hold 800,000 lbs of a grain, it can be estimated that a lot received on a certain date could be safely dropped out after a period of time.

4. FiFo. The implementation team has this on their list of options but I don't see how this can provide any meaningful traceability.

5. Something I am missing that is not listed above.