My first instict is that on a whole..they are not going to ever have strong value. There are always exceptions in any genre but if you plan on bulk registrations of these I'd be very cautious. The LLLL.com market crashed quick and never recovered. CCC.com's are stagnent. CCC.net's are reg.fee even when sold out.
Are LLLL.net's sold out yet?
Only one truth has held in the market. Premium keyword dot coms.