Seconds to minutes. The virus is quickly inactivated by drying.
It is however possible to get AIDS from a toilet seat if you sit down before the last guy gets up. 
Has anyone ever gotten HIV from sharing razor blades?
Don’t know for sure, but my roommate and I have separate razors, where before my diagnosis we just used whichever was closest. My toothbrush and razor are now uniquely identified with red tape, just in case.
It’s possible to transmit HIV anytime you blood to blood contact. HIV is fairly fragile, bleach easily kills it. Alcohol can kill it. Studies at the University of California Dental School showed alcohol at 24 proof will inactivate it, but not kill it. Alcohol at 100 proof will kill HIV in lab tests within five minutes or less. Bleach is the recommend way to sterilize anything suspected to be exposed to HIV.
Saliva also inhibits the spread of HIV, NOTE it does NOT kill it or inactivate it, but makes it harder to replicate.
To properly sterilize with bleach
Clean with water, for needles flush at least twice. Fill needle and shake 30 seconds. Squirt out water away from clean water supply. Repeat once again
Fill needle or put instrument to be disinfected in FULL STRENGTH household bleach. Make sure it’s filled all the way or covered completely. Shake for 30 seconds, (or soak for at least 30 seconds). Then repeat two more times. Three times in total
Rinse needle or instrument at least five times, each time with clean water, to rid all traces of bleach. Rinse AT LEAST FIVE TIMES, this is important to remove all traces of bleach.
To clean floors or other surface areas, bleach alone is fine. It doesn’t need to be left to soak on floor as it’s much easier to kill the virus when it is spread out as opposed to being concentrated in needles or other implements.
It’s considered rare but it may have happened. In Australia an 18 year old girl was infected with HIV through sex. About a year later her 16 year old sister donated blood and was told she was HIV+
The subtype of the virus were matched and found to be the same. The only explanation anyone could find was the girls used the same razors to shave their legs.
The younger sister never had sex, or did drugs or had any other risk factors.
However there are lots of other examples of people sharing razors, toothbrushes and such and not passing the virus.
So this shows anytime blood-to-blood is involved it IS possible but not likely
To be clear, HIV is the virus, not AIDS.
FWIW: I was in a sexual relationship with a HIV+ guy for 6 years. We lived together, shared food, utensils and colds. We practice safe sex most but not all the time. I am still HIV-.
We also had a cat* for awhile, so there was some bloodletting too.
*They are nothing more than very cute fur covered fangs & claws with an attitude.