I figure when he's starting to realise that the wins are not really wins, he will also realise he's not been "getting one over" on us.
At the same time, there are always things you can negotiate on. E.g. I don't care if he's up until 10pm if he can prove to me that he will consistently get up on time and do well at school despite staying up late.
We're already playing that with him: We point out in the mornings if we notice he's tired that he seemed to have gone to bed too late, and we "trade" going to bed earlier on school nights against staying up later during the weekend. As a result he sometimes tells us he wants to go to be before the agreed bedtime.
And I'm willing to be flexible about all kinds of things as long as he's giving us something reasonable in return. E.g. he gets weekly home work, and so I'm willing to skip on doing it one evening if I can trust that he will stick to an agreement of more than making up for it the following evening (and if he doesn't, he knows the consequence is much less freedom for a long time).
I've no doubt I'll still have plenty of challenges down the road.... And he is already a master negotiator, though sometimes he's trying to be too wily for his own good and sometimes ends up talking himself out of a good deal because he doesn't yet understand all the options well enough. So he gets maths lessons this way too...