Construction project 400k: How much to add floors?

And do you really want to pay it off for that long? If yes, then economically speaking I don’t really understand that, since your income is high and you haven’t taken out much credit.

For me, the security is simply worth it. 30 years is a long time, a lot can happen. Of course, we have secured against a possible death, but what about illness, a child getting sick, etc. There are too many cases where two incomes can quickly become just one... I have experienced that in my own family. And why take that risk? For 0.1 or 0.2% less interest? My dad paid >8%, he laughs at our interest rates. Besides, in this low-interest phase with many money and pension investments, I currently earn more interest than I pay for my loan. And I am (almost) sure that in 15-20 years it will be significantly more profitable for me to invest my money rather than pay off my loan as quickly as possible. I understand that this isn’t everyone’s thing. Admittedly, I also spent a long time thinking about it and often considered financing shorter and "cheaper." Today I am glad about how I did it, would do it again, and would recommend it to anyone.

Two notes on this, I can't help it: 1. People who used to have high loan interest rates also had higher interest rates during the accumulation phase, had lower manufacturing costs, had lower incidental costs and did not have the necessity to put 4% of their gross income into Förderprogramm der Finanzwirtschaft private retirement provision. I will leave aside the issue of real wage development. 2. It may be tempting to repay less and instead invest one's money. However, this is always (unavoidably) associated with a higher risk (than in the case of repayment). If that is clear, everything is okay (just doesn't quite fit with the security concept in financing).

Because of 0.1 or 0.2% less interest?

For a 0.1% surcharge, I would also take 20 years instead of 10. But we're rather talking about 0.5%, and you probably know that too. Overall, your argument doesn't make much sense to me. Bieber has already said the most important thing. Especially with you, where you want to shorten your calculated term (special repayment), but still pay for 30 years.

Consumers should also change their perspective sometimes: Why should banks actually offer (supposedly) very cheap 20-year terms if the future interest rate level is supposed to be so high? Do they have no businessmen there but Samaritans?

Because the bank has also fixed the conditions for itself for 20 years in the here and now.

Exactly. And that means: The conditions for 20 years are market-based and not "particularly favorable." The banks set the interest rate based on their own risk analysis.

Just as market-appropriate as 10-year loans are.

But there is also a difference in the type of bank and where the money that is lent comes from. There are institutions that are strong with 10-15 years and others that are good with 20-30 years.
For example, we have a 20-year fixed rate from an insurance company and 15 years would have only been 0.1 cheaper, 10 years another 0.1. They use their own insured funds for the loans and like to invest long-term.
Another insurance company, which unfortunately ultimately could not make us an offer, would have had a 25-year fixed interest period for the same conditions and I think a 0.2 surcharge on 30 years.
Then there are sometimes constellations where the 30-year full repayment loan is cheaper than the 20-25 year regular annuity loan.