What should be the long term behavior of a browser after a user chose allow/deny?

I was wondering what is the expected behavior of a browser after a user
choses, say, "deny" in the geo prompt. For how long should this choice
persist? Should it be:

+ Forever?
+ For one day?
+ For one week?

Looking at different browsers, it seems every device treats this different.
For instance, the following browsers won't ask for:

+ Safari: One day
+ Chrome: Ever again.

My question is due to the fact that I have a website and some users are
reporting that they do not see the prompt anymore and I'm not sure how to
make the prompt show again. (Doesn't seem possible from the client side
logic. One thing Chrome does better is, it provides an icon in the address
bar where you can reset your geolocation permissions.

-- 
Samuel Roldan
www.sam3k.com
Tel 917.880.2580