Delete them and give as much 1h ones to players as the deleted ones worth.

There is no reason to have 4 different type of training books, you can already stack it's suration.

Also make them soldable to vendor.

Better yet, let us exchange those books or all training books of all types for marni's playground time. That way if we want to do another hour there, we could by trading in said book.  I think my florin storage is nothing but those books since I never use them lol

Or allow us to exchange those books for one hour scrolls.  Sometimes, I like being able to just click on a couple for huge chunks of time if I'll be AFK for a couple days.  Being able to exchange for smaller units will allow for flexibilty, which always makes life better.