First and foremost and above all, get this point into your head...it takes work.
Let that point sink in.
Now that you have accepted the primary point, lets move on from there...it takes exposure.
This is where the work (lots of it) comes in.
Take everyone of your domains and list them for sale and for parking at...sedo.com, bodis.com, namedrive.com, afternic.com, parked.com and others.
For each domain that you upload, you will need to set keywords...keywords are what attracts the traffic. Without traffic, you have junk.
You will need to upload and set keywords at each place you list them for sale or for parking.
Don't concentrate too much on where to park at the moment. The key is to list them in as many places as possible to get the exposure.
You mention that your involvement in the internet of 15 years. If you can make sites, then make another site with your domains listed. Again, exposure.
Okay, domains listed at as many sites as possible, keywords set for each individual name at each site...maximum exposure achieved.
Now you can move on to selected where you want to park your domains.
If at sedo, fine...set your DNS to sedo servers.
Look at your traffic after 30 days.
Take your names that have no traffic and move to another parking service...you already have them listed with their keywords. Just because you got zilch traffic at one place does not mean you have no traffic. Some parking companies do better with foreign traffic than others (bodis is a good example).
Got traffic but no conversion? Perhaps the keywords suck. To help determine keywords, park them at namedrive. Namedrive is great at listing what keywords your actual traffic is looking for. This can be invaluable in taking traffic and actually converting this into clicks. Clicks = $.$$
Give yourself (and your names) the benefit of the doubt...allot about 6 months time to try out different parking services and setting/resetting keywords.
Yes, ultimately those that have little to no traffic are not worth renewing or keeping.
There is NO APPRAISAL service worth paying for or even free (ie, estibot).
The end result is you have done the work necessary, you have exposure of listing these names at multiple sites (thus greater indexing on the search engines), and you know which ones MIGHT be worth holding onto.
Don't expect your names to get offers or sell without putting some work (A LOT OF WORK) into marketing them.
If you are asking these questions now, then that is proof positive that the buyers are not knocking each other over to get your names.
Work + Work + Work = Exposure.
Exposure = Traffic + Offers
No Traffic + No Offers = Junk Dump