There is no definitive answer to this question as it depends on a number of factors, including the size and layout of your bathroom, the style of your vanity, and the type of lighting you want to use. However, as a general rule of thumb, you should aim for around four to six lights over a 60 inch vanity. This will provide enough light for most tasks while still creating a warm and inviting ambiance in your bathroom.
If you are unsure about how many lights to use, it is always best to err on the side of caution and go for more rather than less. You can always dim or turn off unused lights if they prove to be too much, but it can be difficult to add additional lights once your vanity is installed.