As a follow-up to my previous response, the term "Period" has multiple dictionary meanings. It can mean simply a duration in time (e.g. 7 days), or instead an anchored duration in time with a specified start and end time (e.g. the period from 2015 Sep 11 to 2015 Sep 18). If your model needs both concepts, I suggest you use Duration for the former and Period for the latter (as recommended for SQL). In that case, you could rephrase the fact type under discussion as
Year(CE) limits car rentals to maximum- Duration(days:).
This uses hyphen binding to shorten the predicate reading while still ensuring correct verbalization of constraints (e.g. Each Year limits car rentals to at most one maximum Duration).