I assume that you probably have images who's retention is longer than 2 years. Are you using the -U flag?
Depending on how long it takes, I would execute the command and direct it to a file, then while it runs take care of other things you have going on, then parse through the file.
You say you are not a huge command line person, so just in case (and I"m assuming you're working in a UNIX environment, you didnt specify) you can execute
nbstlutil -list -U > nbstlutil.output
Then just "more nbstlutil.output" so you can look through your file for what you need.
If you are needing something else, then maybe someone who is more familiar with SLP's can chime in. That is just my 2 cents from what little familiarty I have with SLP's. We're going to implement then at some point in time.