whether I have 300k remaining debt after 15 years, or 350k after 10 years, the interest rate risk is almost the same in both cases (16.6% difference in remaining debt)
but to have 16.6% less risk (slightly less remaining debt), yet pay over 50% more in interest in the first 10 years, makes absolutely no economic sense. So as calculated above, paying off 50k more and paying a 21k surcharge for it doesn't really matter...
either I can reduce the risk by 80-90%, i.e. pay off almost everything during the fixed interest period, or not.
and then refinance into a cheaper loan after 10.5 years?
for that, the interest rate would have to be below 1.4% for it to even make sense, otherwise you still throw 21k out the window...
one should consider what is more likely in 10 years?
interest rates below 1.43% or above?
if you notice that interest rates are rising (this does not happen overnight, but is a slow creeping process) then you can already react in 6-7-8-9 years, and directly arrange a forward loan for the period 11-20 or even 11-25 years.
I already mentioned the advantages earlier.