With my condominium, it was as follows:
Fixed interest period 4 years, annual special repayment 10% instead of 5%.
Duration without special repayments would be 6 years, 4 months.
Actual duration will be 3 years, 8 months.
At the very beginning, I couldn't make any special repayments because the money went into renovation and furnishing, but since then I have been using it fully.
The financing amount was of course only a fraction of the upcoming house project.
The idea is to keep the installment manageable and repay a high amount as special repayment. The money that is free during the year would not go on luxury vacations or similar things, but should simply be available during the year in case unforeseen expenses arise. If the year is over and the money is actually "left over," then it goes into the special repayment. At least that's my way of thinking.
However, it is also true that even the standard 5% with a financing amount of, say, 200,000 or 250,000 is already an amount that you first have to save on the side.