I'm one of those anal types that will use solvent and remove all bearing grease then re-grease bearings whenever I change grease types or do not previously know what type grease was used.

It is true that some greases don't play nice together, however, this is probably rare. If you read the label on most greases it warns against using them with other types.

To be safe, you can clean out all the old grease and re-pack with the grease of your choice. I prefer to use a sticky grease like StaLube marine grade.