Age per se is not an important factor, but perceived age, as related to perceived era is a relevant factor.
For a Javanese keris conscious person the base system of reference is the tangguh system, and this tangguh system is based on a belief system. Here is a link to a page in my site that gives a brief outline of tangguh:-
http://www.kerisattosanaji.com/keristangguh.html
In respect of the Javanese artistic appreciation of keris art, the first principle is to relate the blade to human body language and form, as understood within Javanese society. Following on from that, more universal standards that apply to excellence of craftsmanship and achievement of pre-determined objectives can be applied.
The ideas of a blade being "empty" or of being "alive" are largely dependent upon individual perception within the framework of the keris belief system. To a degree this can be regarded as a culturally related concept, but instances have occurred where people outside the Javanese culture system, and with absolutely no understanding of it have encountered a perception of a presence related to a keris.