>>530977306
>>530977953
>>530979049
I actually just did some math on that. One thing you should know is that different servants have different bond amounts to hit bond 10, with 1*s being the least on average and 5*s needing the most. To go from bond 0 to bond 15 needs about 700-750 days, assuming bond only from OC quests at highest bond bonus. With a party of 5, that's 30 quartz for each bond 11-15 level for 30 * 5 * 5 = 750 quartz over about 700+ days or about two years.

so tldr if you want to maximise bond quartz
>use lower rarity servants
>get every bit of bonus bond as possible
>bonding from 14 to 15 is slightly less efficient than 10 to 14 quartz wise so stop at 14