I started collecting "things" after married and with kids!  
 
From precious stones and knives, all of them I always wanted to know the details on how to identify the material I collected.  
With knives, I'm interested to know the material used and what's the difference / advantages with other materials - so I collect a few different type of sword with different type of material -and also tried to make knife as well.
 
Now, with the keris - the same cycle as well, I do not start with buying all old / antique keris on the market because I personally believe 90% (normally I would say 99% 

 ) the keris on the market are recent make.  (this is purely personal opinion).  The old keris I'm referring to is before 1800.  Even early in 1900, I believe people already make "created" old keris as well.  How many people in the old days have keris made for them with kinatah on it? I believe in the old days, the keris (as a pusaka) only made by order and shown to close relative only.  Other keris (as a tourist keris - nowadays) also plenty during that era.
 
I like keris from art and the time spent to make one.  I personally like to know more about the material first, asked the maker how he made and what material they used, choose the warangka/pendok material or design, etc.  Try to introduce some new material and see the difference.  All this experience, I can not get if I bought old keris.  
 
I collect keris if I have the "feel" that I like it, the model, pamor, "feel" when handling the keris, it does not matter if new or old - as long as within my "knowledge" of keris at that time...  

  I even buy a keris (was told old) but I know it recent made... as long as I like it... simple
 
cheers..