It's capped on 15k, and there are ways to gain (of course, with a lot of efforts) up to 50k at least, maybe more. So, I've stopped looking at things almost completely after hitting 15k observe exp, and not motivated for a futher explorations except for the getting explore exp. Of course, there are some fun aspect of the explorations, but, for instance, I won't assemble a party to go to the Octagonal tower again, because I know this area for 100%. Otherwise, I would. And I would examine things - and maybe I would find something new, as happened.

So, my suggestion is at least to add 30k and 50-60k observe exp goals. Okay, if there is a deficite of EP must be in the game for some weird and twisted reason, it could be a small value, but even that would definitely make the explorations/observations way more fun and tempting.