Personally I negotiate,
So to stay always able to negotiate. I don't do them above attrition 8
I can go up to 18 attrition (with negotiations). As you may notice, Battleground gives you
• bad luck sequence (you never guess right)
• average luck (you guess, but not very good)
• luck .. (but spend a lot of goods)
• lucky star (you finish negotiations in 2 steps, or only 2 goods are present in negotiations after 1st round).
Level of luck definetely changes after you exit / re-enter Battleground. It might require do some actions - e.g. visit your colony or guild expedition or event screen (if present) - and then re-enter Battleground.
It's quite a pity to quit negotiations when you're on a roll - e.g. you're given luck or lucky star you fly like an eagle, solving negotiations one after another in non-stop way - but soon you're out of goods and had to finish negotiations.
Also, if you push hard enough on Battleground, you need 3-4 days of production for 1 (one) day of hard negotiations. If your small guild opposes the big guild, you need to got 12-14 of attrition, just to hold what's yours on a map. Daily, I produce at least 120 goods of my age (Gold, Honey), and 120 goods of the previous age (Ebony, Jewelry), very actively trade/exchange it for other goods required. But if I play hard in Battleground - I need strong support of my guild mates (e.g. line of supply of goods), to continue.
P.S. And in these days, when I was doing up to 16 ... 17 .. 18 attrition, we had a sronger opponent, who was conquering our sectors quicker than we were taking new ones - that was a mess, we lost the Battleground, and then decided to skip next Battleground, just to re-fill our storages.
That's how it work now - if you play very active, you need those 10 days of next battleground just to re-fill storages for battleground, coming in 3 weeks after.