That will first require proper tracking of how many pvp fights you currently have (gained from familiar usage and consumables, and actually making sure to check how many you have to begin with). I think I have most of that done on my system, and the parts I don't have coded probably won't be too hard.
On the other hand, since you can display remaining pvp fights on your charpane, this seems like it would be as obvious as a reminder that you have adventures remaining.