This might purely be a hunch, but for the 3 FATEs required to finish a book on my first four? I always camp on where the FATE usually pops out and all the time, roughly within an hour (mostly less than 20 minutes after one just shows up), another one will pop out ready for me to charge in with my stardust blazing. Can it be that proximity of a player to a FATEs location increases their frequency? Im not sure, but experience tells me somehow it 'might'. Waiting is no problem for me because im a crafter so all i have to do is bring mats, craft at a safe spot until it pops out. It takes so much time anyway to run from towns to the actual site. "Raid" FATE's are the worst where their location is too remote to get help from especially when there is not a soul around. Eventually, soloing becomes the only feasible way to deal with it and that requires all the time you need before the timer runs out.