For the past few days my luck has really spiked, but before that, I barely got 1 a week. So, I'll average it out and go with "Once a Week."
Also, just a tip, getting a Lost Relic comes down to two things: luck and determination. Luck can't be changed, just be in the right place at the right time. Yet being determined is also the key. Just keep at it, and in time, it shall come.
