Yes a unusual situation as we rented a villa two years back and didn't have a clue.
Did a lot of computer research, found some that seemed to much and finally made a decision on what to leave keeping in mind that we were extremely self sufficient
and did not need any special attention.

Our house keeper would clean every day but we did our own dishes and such.
She would stay about 4 hours a day and pretty much did just the basics like making the beds, changing towels and sweeping and mopping the floor

On the day of departure our housekeeper was extremely happy and said it was the most generous gratuity she ever got
I did not think I went overboard as I do in a restaurant for good service
I was even more surprised since Julian Lennon and Kid Rock also had stayed at the Villa in the past

Besides showing the Villa on the first day and collecting the keys on the last day, our concierge did very little

I know we tipped our visiting chef $150 for one nights dinner for 4 guests, but he was excellent and did more than could have been asked
He was also very reasonable priced, less than what I charge here in the states

I guess you could figure out what you would leave for a night's stay in a hotel and add in for the extra bedrooms and remainder of the villa being cared for

Please keep in mind that I have been in the hospitality business for over 40 years and have appreciated all my guests that been so generous to me so I guess I am just passing it along

If you really are worried, I would respectfully ask your housekeeper what is fair depending on the relationship that you have during your stay

In all honestly, you can never over tip if you feel it is warranted