I dont understand how this is more work. You said that you get notifications every time there is something logged or changed on the caches that are all ready in the bookmark, so if you do the steps that you just mentioned shouldnt the new caches that need to be added to the list be at the top (under the events) of the first page? What about pocket queries? Can you filter it by dates if you do a pocket query?
This seems to make MORE work for me, not less. How about this. Go to Geocaching.com, Click "Play, then "Find a Geocache". Click "Take me to the old Search". Choose "Latitude Longitude Search" and put in N29 45.400, W095 21.800 and a radius of 50 (or 75) miles. Click "Search". On the resulting page, click the words "Last Found" at the top of that column, TWICE. This sorts the results with the longest unfound at the top. Below the events, about halfway down the page, will the the start of the list. Feel free to go back as far as you want to see unfound caches. Had I stuck with the old method this month, it would have stretched to the bottom of page 9.
I think that you should make 2 separate bookmarks. Only list the 3+ year caches but also include the 2 year caches in the post. That way we can still work on the 2 year list and they hopefully never make it to the 3 year list.