After 365 Days full-KBackup, no incr. possibel. Why?

I’m from Germany using KDE with OpenSuse and KBackup.

Why ist’nt it possible to make an incrementally backup after 365 days?

I’ve not so much changed data and not enough space on my NAS.

Is it possible to make a zero (0) by ‘days’ to allow a incremental after 365 days?

kind regards