How soon after an upload will you be notified if your work unit was a prime?
It depends on how long it takes for your wingman to return his result. The notifications only go out after the tasks are validated, which takes at least two matching results.
Also, the notifications don't go out automatically. They need to be invoked by one of the administrators. The prime reporting process is complex and often requires manual intervention, so it's not completely automatic.
My lucky number is 75898524288+1 (I am NOT an administrator anymore, so please don't PM me with questions. I can't help.)
One last question: Once a prime is confirmed, does primeGrid automatically add 2 to it so it can determine if the resultant is a twin prime?
On SGS primes, yes, it's a mixture of your client and two additional tests on the server. For any other subproject we do not normally check to see if it's a twin. At one point a year or two ago, I took it upon myself to test every prime we'd found up to that point to see if it was a twin. None of them were. More than half of them were divisible by 3 or other small factors. I'll probably do it again some time in the future.