It depends if the historical lead data is still of value to you or your sales team. If you've dramatically changed your scoring model and thresholds, it may be problematic to retain the historical lead data. That said, you could create a secondary lead score field for legacy data, and write all your historical lead scores to that. You'd then be safe to zero out the primary lead score field, but you'd still have the legacy score data if you ever need it.
There are many threads on Re-scoring methods. Please take a look at those as well.
- Setup the new model
- Create it in a new Program
- find a quiet weekend to do this and warn sales they may get MQLs.
- turn off the MQL sync if you do not want to immediately push all records.
- export Email and Score fields for safekeeping.
- erase all scoring fields
- turn on behavior
- rebuild demographics or whatever
- take a look at the data.