I used to try to compare my own overall times, or average speeds on these events, but you can't really. A lot depends on the weather, how often and for how long you stop or get held up, or whether you get lost/miss a turn etc. I also try to compare myself to how other people around me on the event seem to be doing. Not being passed at all on climbs perhaps means I am doing OK, but of course you don't know if the people around you are having a bad day or "saving" themselves or just enjoying a relaxing day out (since they're not racing), so it still doen't mean much. At the track last night (derny session) I was rather flatteringly told again that I should go in for some road racing in Cheshire this weekend and "would not get dropped". We are away anyway, but I still think I might not cope too well with the sudden changes of pace (I'm not a sprinter) despite being a decent "steady"/TT-type rider - racing is very different. I think that comparing yourself to others is little more than guess work, unless you actually race against them!
BTW - take the speeds some people talk about on-line, with a pinch of salt. Most of the people I met didn't go anything like as fast as they'd claimed they did! I think some people confuse average speed with maximum speed, or with the speed they happen to be doing when they look down at their computer! Many people also do not mention the average speed difference between a short ride and a longer one, or a flat ride and a hilly one.