The reality is that charging without using a balancer is riskier than charging with one.

Personally I've never used a balancer (I don't even own one) even on packs up to 5S, BUT understand that I'm taking an unnecessary risk. I minimise that risk by only using a small number of "quality" packs and only charge at 1C. What I don't have is 20-30 different no-name brand packs in varous states of puffiness with internal IR's all over the place charging at 5C.

Probably once every 6 months I'd check the balance of a pack with a voltmeter as the pack reaches the 4.2V/cell bit just to make sure all the cells are still getting to 4.2v/cell under 1C charge current at about the same time. All my 2S RX packs are charged at 1C in the plane BUT if I were going to charge my 2S RX lip-po's at more than 1C I'd definitely fit an external balancer port.

One side note is that while somebody was flying at the field one day I noticed smoke rise up from his charger and the charge leads to his plane start to melt. I quickly unplugged everything and let him know when he came back, it turned out the charger had failed and excessive current had flowed though his NiMh rx battery even melting some of the EPP foam it was wrapped in. So no matter how careful you are, in-plane charging is never risk free and made me think about fusing my charge leads just in case.