Re: death of sperm
It only takes one sperm to make somebody pregnant. In theory, though the odds are low, a single sperm placed in the vagina (through clothing, by a finger, whatever) could fertilize an egg....so don't take any chances if you don't want that to happen.
At normal temperatures in a dry environment, I would be surprised if sperm lived anymore than 48 hours outside the body. however, add moisture to the environment (like actually being in a female) andit could stay alive for at least 3 days, probably more. If you are in a hot tub, sperm will die much, much faster. Sperm don't like high temperatures.