What worries me is giving up 6 months or a year - and having a challenge getting back in the work force.
I'm a little older and am at 73x bare bones right now, but closer to 43x what I expect for a more likely and practical FIRE budget. I considered taking a summer or longer off before myself, but while I wasn't concerned about finding another position later on in my technical field, I highly doubt I could have gotten paid as much as I was being paid on my current job, even if I was to move to a HCOL area, which would cut into my savings rate going forward, plus I would have lost the benefits I built up over the years such as vacation, retirement vesting (of company match), bonuses, etc. not to mention being the top dog in my position. So I decided to just keep working a few years longer while I have it good at my current job so that I could FIRE later on with little chance that I would "need" to work again. If you're willing to settle for a big drop in pay when you re-enter the job market, go for your gap year. Just think through all the angles and enjoy!
What is the point of trading your healthiest years for more money when you are at a 2.5-3% withdrawal rate?
I don't consider the years I've worked to have been "traded" because I didn't give them up just for money. I enjoyed them, and I wasn't working 24/7, and I actually enjoy my job a lot of time as well. If I was working 60 hr/wk and hated my job, that would be a different story. I only work about 40 hr/wk and have weekends off, not to mention a nice amount of benefit time, while saving over $50,000/yr in recent years.
I actually plan to go with a 4% WR. If I had gone with a 4% WR with 25x FIRE expenses a few years ago, that would have given me about $500/mo extra over bare bones, which I could certainly have lived on, but that's a tighter budget than I wanted to have in FIRE. By continuing to work, save, and let my stash grow the last few years, a 4% WR rate today would give me a cushion of about $2000/mo over bare bones spending. My early FIRE timeline is 22 months from now, and if I save an expected $90,000+ in the next 22 months, that will add another $300/mo to my cushion at FIRE on top of any investment gains, so $2300/mo total cushion, not to mention a boost of about $100/mo in SS benefit (around $1400/mo SS total) a decade later in year 2017 dollars. On top of savings, by avoiding draw down, that's $3500/mo (4% WR) = $77,000 that stays in my stash as well because I won't be drawing down for 22 months.
The cushion will give me more options during FIRE as to what I can do to enjoy retirement without being restricted by funds. For example, I plan to do more extensive traveling which I've been putting off for years. Another use of a nice cushion would be for relocating. I'm in a LCOL area now, so some areas I am interested in would actually increase my monthly expenses considerably despite downsizing. I don't know that I'll do it, but I want to keep the option available. And once I FIRE from my enjoyable decent paying job, I don't want to ever have to work again in the future at a much lower pay rate just because I come up short due to higher expenses, and a nice cushion helps avoid that. It's much easier for me to build up that cushion now than try to make up for a lack of one later on.
Another advantage of having a nice cushion has to do with investment growth in order to maintain a 4% WR, primarily with expectations of growth in the next several years when you consider things like high CAPE and "sequence of returns risk," which are covered extensively in other threads here. In a bear market, I will have more flexibility to cut down my WR considerably while still covering my necessary expenses.
Edit: For further clarification, the multipliers and WR % are only in relationship to my investable stash including retirement accounts - it excludes my emergency fund and home, which is paid for. The $90,000+ expected savings over the next 22 months refers to actual income saved from my job including employer retirement fund match, not dividends, gains, etc. So those would be on top of the savings, plus that's an additional 22 months that I'm not drawing down at $3500/mo (4% WR), which keeps $77,000 in the stash during this time on top of savings and potential gains. If you discount unknown investment gains/dividends from the calculation, the savings and lack of draw down alone ($90,000 + $77,000) is $167,000 stash differential in 22 months vs. retiring and beginning a 4% WR today.