My estimated FIRE date is a little over a year away. I have a monthly barebones budget that includes all my expected bills over the long term (including infrequent things like costly home maintenance) and averaged out per month.
The remaining figure after subtracting barebones from my take home pay is for saving/entertainment/buying non-necessities, but not broken down into separate line items. In almost every year, I saved at least 90% of it.
When I FIRE, based on a 4% WR, that remaining figure after subtracting barebones will be smaller, but traveling will probably become a new significant portion of that along with more entertainment and still some splurging on misc.
So, as a single person, that will provide about $30,000/yr. for travel/entertainment/splurging, but it's not broken down into separate line items or to a monthly basis. In fact, some vacations are much less expensive than others, so I might spend more one year due to one or more expensive vacations, then cut back the following year with some low cost vacations.
Wild card for me that could change things up is the possibility of selling my home, maybe some slow travel without a home base for an extended period of time, and eventually re-locating.