I have run up to 22.2 volts with a 9L through the stock slipper, so it can handle a bit of power. I haven't run the "big power" that you run, though! Of course, I haven't used the stock slipper for a while, since the strobe is worlds above.
I just came back from holidays, and I run my Revo hard, for 2 weeks almost every day. On tracks and around the house. I run my 7XL on 14 and 16 cells. I still have the stock slipper, no troubles so far. But I'll get a strobe anyway.
However, on the smaller tracks I used a 18/66 gearing (14cells) and on the big track I ran the 20/66 combo. If I ran 16 cells I stayed with the 18/66, too. My temps never exceeded 70 degrees celsius, even after two runs back to back. Amazing!
When my truck was dialed in, I could keep up with 1/8 buggies. Believe it or not. Even passed a properly tuned O.S. buggy on the straight on 14 cells.
On 16 cells its plain insane!