Excellent discussion!The three things people dont factor in, tend to be tax, the state pension and the usual reduction in spending from your late 70s until you need care when doing the calcs.
I calculated my outgoings in retirement (not there yet but its good to know) and they are around £2400 per month in total for the two of us, assuming we dont downsize. This covers everything including running 2 cars, insurances, gas/elec, rates, a bit of social spending, season ticket etc. The state pension alone for a couple, works out at around £2100 per month from next year and is currently inflation protected due to the triple lock. So from 67 we would need to find 300 per month (adjusted for inflation), to cover the basics.
Outside that, having a big pot really only buys you an earlier retirement and/or more luxuries when it comes to holidays, eating out, gifting to family etc. So the only real question is how early do you want to go and what that looks like in terms of fun money. As you say its different for everyone, some want to be travelling the world in luxury, others are happy with walks in the pennines and lake district.
If I was happy with the minimum I could probably call it quits as soon as I hit my 35 yrs of paying in which will be in 2 yrs time, in reality I will probably be ready to give up full time work at 58/59 and maybe just do a bit of consultancy to keep my hand in for a few years, but give me flexibility to take extended breaks.
Whilst the 4% rule is OK, the chap who thought it up now says its too conservative as long as you have the stomach for a higher equities holding, remembering that the 4% rule is there to also preserve most of your original capital.
Looking at strategies I think I prefer the guardrail based rules like Guyton-Klinger which provides a bit more adaptable approach, but with a few tweaks around the edges.
I agree with your Guyton-Klinger, or guardrails, approach, with the bucket strategy back up and it’s what I’m using to plan my own retirement.
With a relatively strong cash cushion, it allows for a more aggressive guardrail approach, which (in the absence of historic negative outcomes over an extended period) should result in a very favorable outcome, including principal growth of a well-diversified equity portfolio.
I’m not sure if the UK has RMDs, so I’m not sure whether that’s an issue for people, but it can be an expensive wrinkle which, if addressed by increasing the high limit of the guardrail, could allow efficient conversions into taxed income. This is a future problem I’m looking to try to avoid, but which seems almost insurmountable given our specific position!
Regardless, I really like the Guardrail approach rather than the 4% Rule, but I also understand the 4% Rule is a good starting point for some people to do back of the envelope maths to give them a rough idea of not only where they are now, but also what they need to do to get to where they want to be.

