@Jacqueline I try to supply nice stuff too, including olive oil, as well as coffee tea, common cooking herbs, butter etc. This is because as a guest it is frustrating to pay for a whole package/bottle of something at the grocery store for a 3-day stay. (And I buy organic because this is what I buy for myself and I am committed to eco-friendly consumerism.)
For longer stays my thought was people would be buying their own supplies because they would in fact be using it up. Since there is no way to be politely clear about this, with things like olive oil and balsamic vinegar i have a smaller sized attractive bottle set that I keep refilled so they cannot use an entire litre.
I find the pricing market here very tight so I can't really afford to give everybody a 10€ bottle of olive oil that visits, including longer stays, who are getting a discount anyway
As someone else in this thread said, leave an approximate amount for the length of the stay.
As a guest I bring my own coffee because I want organic and am picky... same with shampoo.