I was thinking 30 to 40 relics. But hey I'm just a player, and not a member of a top ranking guild 
Those back and forth captures in Moot Forest were kinda fun yesterday... At least until a few guilds started sending people who were level 60+.
Which brings me to one possible suggestion (and with over 10 pages of replies in this thread, no, I didn't have time to read them all to see if anybody else suggested it yet), would be to make a level restriction for each relic based on the average size of players who normally hunt the areas they are located in. The Moot Forest relic where I was yesterday, was all fun and fair for the first 30 minutes or so, but then much larger players from the top few guilds wandered in and took it... It then becomes nearly impossible for anybody else in the area to even try to take it from them. That first 30 minutes seemed fair and fun because everybody in the area up to that point was in the level range of 40-44 ... There may have also been a 45, I'm not entirely certain. Additionally, of all the guilds I saw there, most only had two members at a time taking and holding the relic... Perhaps this would suggest that maybe the attack groups and number of defenders should also be reasonably limited in some way.
As I mentioned to my guild yesterday, I imagine that the way these are going to end up, is when a high level player gets bored, or tired of playing FS, and only logs in maybe once or twice a week, their guild will have them sit on a relic making automatic defense every time that guild captures the relic... If they are even able to lose it with such high level, inactive sitters.
Also, the safe period suggested X number of
hours seems far too long. That means that out of all the guilds wanting relics and wasting time in the area to even try to capture one, only the one that clicks first has a chance to take it and all others only get one chance for that one fastest click, in a full hour+ amount of time waiting. I'd say 15 minutes may seem kinda long in some cases, but reasonable... Maybe even 30 minutes if we're pushing it.