I'm running D&D 5e. My players have recently come into possession of a Manual of Bodily Health. The very first thing they thought of was how to abuse it. They are planning on reading it and then burying it in the Feywild. The time dilation in my world means that every day in the material plane is years upon years of time in the Feywild. Rather than having them stack their Constitution bonuses infinitely, how can I reasonably limit this?
The description of the item is as follows:
This book contains health and diet tips, and its words are charged with magic. If you spend 48 hours over a period of 6 days or fewer studying the book's contents and practicing its guidelines, your Constitution score increases by 2, as does your maximum for that score. The manual then loses its magic, but regains it in a century.
The Feywild has been a realm where time flows differently. I used the example of taking a couple of minutes between entering the Feywild has been a total of 2 weeks of waiting inside of the Feywild for the rest of the party to join.
This manual was an item they rolled on a magic item table, and therefore something I hadn't properly planned for. Considering its already very powerful effects, I'm worried about the players following through with their idea of "Let's bury it in the Feywild and use it over and over again! I bet this is something the DM didn't think about!"