Map/Reduce Stored Data Limit

I am trying to write a Map/Reduce script to process ~5 million (custom) records. Right now I have a scheduled script that can knock out 1.6k records per deployment that is chipping away at that number, but not as fast as I'd like.

My attempts at processing the records via Map/Reduce cannot get past the input stage unless I hard code a list of internal ID's into the script. The script just runs for 5-8 hours (doing something with the search I pass it) and spits out the following error:

{"type":"error.SuiteScriptError","name":"PERSISTED_DATA_LIMIT_FOR_MAPREDUCE_SCRIPT_EXCEEDED","message":"Stored data limit of 50MB for Map/Reduce script exceeded."}