Need advice for Object cleanup

I would like to clean up old unused Jobd, Jobq, etc. I ran a DSPOBJD to
outfile get lists with the last used date, etc. What gotcha's should I
lookout for basing my criteria on the last date used? For instance, if the
last used date is zero, does that mean it's never been used, or if it's a
year old, does that mean nothing has used it to since then?

Is there an easy way to determine if a Jobd is attached to users, autostart
jobs, etc?

I "inherited" a few messy systems, so I really need to clean up all types of
objects, maybe theres a better way to go about this whole project? Any
other tricks you can recommend?

Thanks, Tim