I get a new manual when I find a new powder I want to try isn't in my books. Or, when I get a new caliber (like the .40 S&W P07) that isn't in my manuals. I'd been happily using the old Speer/Hornady books from the early 80's till I got that .40.
Since then I bought the .357 SIG, fiddled with .300 BO for a bit, etc., etc.
I do a lot of checking of the powder/bullet maker web sites, too, like you mentioned. Just looked up BE86 on the Alliant web site. Got a lb. yesterday. Need to sit down and start working on some 9MM 124 grain loads.
I will admit to comparing info, too. Sometimes it's quite different. I chalk that up to different cases, primers, seating depth, etc. vs. what I have on hand. Starting loads to start, work up, see where the good groups are at.