From the manual "Indexes provide fast and direct database access, but require more time to create and maintain." which you have already identified as the culprit because you have 10 indexes.
Also from the manual, " [A filter] is not used to identify a document or the field is always used with an index field to refine the results of a query. A filter causes a sequential search of the database."
So, there will be a sequential search at retrieval time each time any of the filter fields is provided as input, thus elongating the retrieval times. Personally, I would not remove all 7 indexes all at once without observing the impact on online/real-time user experience. If retrievals are going to be impacted to a degree not acceptable to users, maybe dropping 1 index at a time and observing for a period of few days would ensure you don't rock the boat for users.
