There are statements elsewhere that there's no real point to the HallowNest Seals, and Wanderer's Journals, other than selling them and them being "bankable" Geo.
I'm a completionist and somewhat skilled so I've never lacked for Geo at any point. I recently had 8k Geo despite having bought every item available,
losing 4.5k to the Banker Snail
Paying the 3k in the Wishing Well in the Ancient Basin.
I never had any incentive to sell them, so I didn't.
I've now just unlocked
the Grim Troupe, including discovering the Fragile Charms upgrade
and thus suddenly have a need for VAST quantities of Geo.
Before I sell my Relics, does the game give ANY reward for collecting all of those things and not selling them? Any Achievement or acknowledgement from any characters? Is there any reason AT ALL, not to sell them now?