What are the odds? I don't know. Someone with math skills or the right software package could spit the answer out quickly and accurately. How many times have you seen the roulette wheel hit the same number twice, three times, maybe four times? It's very slim, but it absolutely can and does happen. If you spend enough time in casinos, you will see it happen. Most every day, someone in the U. S. wins over a million dollars on a state or regional lottery. The odds are always millions to one. But they are won.
Spreads, heat? These have never been issues for me at any major casino on a busy weekend night. The only time I was ever backed off a table was at a small casino that was nearly empty on Freemont, on a Monday morning, at $5 minimums. If the count is very high, and The Wyn or Mandala Bay is packed on a Saturday night, I have spread 1-20 with no problems what-so-ever. If I can spread to 20 betting units once or twice and win, I usually color up, cash out, and change Casinos. You simply can't get away with this at The Plaza or Vegas Club on a Monday morning. It's good to be sensible with betting spreads, but don't sell your game short out of paranoia either. I just try to stay aware of the conditions and environment I am playing in, and bet accordingly.
I once turned $100 into $3000 - then gave it all right back, at the same table, plus another $100. This gross act of stupidity took less than two hours and involved too many transactions with the cocktail waitress to count.