Hi Cervelo
If you make the conservative assumption that your investments will do no more than simply match inflation, after taxes and investment costs, then you could afford to spend €28,700 per annum, adjusted for inflation, for 40 years before exhausting your pot of €1,150,000. That equates to a withdrawal rate of 2.5%.
Of course, it's highly likely that your investments will do better than simply match inflation over a 40-year period but you do have to take account of the risk that the sequence of returns on your investments will not be favourable. If a high proportion of negative returns occur in the early years of your retirement, it will have a lasting negative effect and reduce the amount of income you can withdraw over your lifetimes. As such, it would be prudent to make conservative withdrawals - and to maintain a conservative asset allocation - in the early years of your retirement.
It's probably prudent to assume that at least one of you lives to 90, although, again, that's obviously quite conservative. You will probably qualify for a State pension at some point but I would be inclined ignore that for the purposes of your calculations and to simply treat it as an additional safety buffer. You could also probably trade down to a less expensive house, if necessary, again giving you a further layer of comfort.
If you take a marginally more optimistic (but still wholly realistic) view of your anticipated investment returns and assume a consistent return of just 0.5% above inflation (after investment costs and taxes), then you could afford to spend €34,500 per annum for 40 years before exhausting your pot. That equates to a withdrawal rate of 3%.
So, putting it all together, I would have thought that you could afford to retire on the basis of your current net worth with a reasonable degree of confidence that you won't run out of money during your lifetimes.