I have 157 Stamina and usally I run out of Attack first, of which I have 271. I use 80 per round to boost chances of Good communication.
Since we're on topic, I split Attack and Defence evenly, and my leader is Yukari R+. Sometimes people fall for it and attack. Not often though.
Oh I actually wonder something, did you ever managed to get Perfect when you used the Attack power (without the special charm for guaranteed perfect)? I usually only use it for blue ones and leave gold ones to RNG because when it says 100% Good I take it that it means literally 100% which would mean you don't have the chance to get Perfect (and from the blue ones I used with Attack power I never got perfect). And since for gold ones Perfect is like 15 times points of Good so even if I get Normal all the time, having a chance for perfect is really important.
Well using tradable stamina drink for ~150 stamina... I dont know. Take this, if you ever manage to get verified, you can buy the Smile versions of the S-rare (so the 18 cost) for about 5 (10 total 2x for special training) and I am having problems getting those at all from the event and usually have to buy them anyways. Those non smile versions you get from completing their levels are usually 1 drink per S rare. So I usually target like around 10k rank for event to get the chance for the special 10,000 exact rank reward (very slim) and unless you can guarantee rank 2000 or lower, who receive the event 21 cost S rare (that's like 300+ drinks) I wouldn't advise using drinks.
Btw if you are around lvl 80 then I might have been one of the people trying to attack into Yukari R+ with bunch of S-rares hiding behind her when I'm getting affection for low attack idols xD Lost to that few times.
Also I always wondered, what is the reward for defending incoming battle? Do you like get lot of fans at least? Because it really seemed to me that Def is totally useless so I didn't put anything into it. It might be from the old days when costumes might have been important since the rares were actually good, but these days all the rares from that are like 200k money if even. When there are 21 cost S-rares flying around already, those 5 cost rares from clothes/work areas are totally obsolete and I only get them for the album entry (And if the girl is my favorite like Rika, I try to get all her cards, including rares and normals, but for other girls I usually don't bother if they have bad stats)