I enjoy going to Fremont Street, but I hate having to pay for parking and don’t want to be limited to just a few hours. I used to park at the Golden Nugget. Now I park at Main Street Station. You do have to pay when you park ($3 Sunday – Thursday; $5 Friday – Saturday), but you can park all day and get the fee refunded.
To get your parking fee refunded you need to earn 50 base points on your B Connected Card or show a restaurant receipt from Main Street Station or the California for $5 or more. When you park, the attendant should give you your receipt as well as a card with the refund instructions.
The parking lot is at the far end of the Fremont Street area, so it does require some walking, but I find it very convenient. It is very easy to get on and off the Interstate from there. Here is a Google Map with the parking lot (adjacent to Main Street Station and The California):