As it stands I think the three day timer is fine, which is why I made a suggestion for a possible solution that would achieve your goal while at the same time creating greater depth and immersion in game.
It relates as a suggestion for a solution that would expand on an existing "racial" change experience, vampires, so that changing race meant more than just typing in a command or waiting for a three day cool down to change to another or back. It would require a sacrifice of materials, maybe silver and full knowledge of the change about to take place. There would be no more "I picked X race by accident and want to reset it sooner than three days". Racial changes would be made with full knowledge, perhaps with a gradual change just like with vampires, and have an "esc" button available as easy as going back to the alter you used and retracting your dedication to it and to the racial change if you decided not to stay that race during the change process., (not to mention it would prevent the abuse of the mechanic by changing race during a fight to prevent death in lava for non-agni, from light for vampires, drowning etc. or for a quick change for tactics based on poison immunity or to switch for weapons like from elf to dwarf mid-fight to get the most from the bonuses.
I really like the idea of racial try out rooms at info and perhaps make those the only places where a racial change could be made so there are no changes made while people are playing live in the medieval world. Than again, I'm not one to speak much on changing race much as I have remained the same one since I started. If the info option was there I'm sure I would give some of the others a go just to experience them without having to spend three days on each.