Googling on from the german words in NichtBesonders post, I found this interesting
judgement which says (inter alia):
The permanent residence permit also expires due to an interruption of residence if the foreigner is absent from the country for a longer period of time, returns to Switzerland for a limited period of time before the end of six months, but only does so for business or visiting purposes. In such circumstances, it is not the (different) departure times, but rather the question of where you live, that becomes the decisive criterion
So,one needs to take care to be able to definively prove that ones centre of life continues to be in CH.
From what i have understood of CH in 10 years, as long as ALL my global income is credited in my Swiss bank, and i pay my tax chuffs, i'll be fine ;-)