The calculation is simple. First, figure out how many "tries" a computer can do per second, minute, or hour, etc. Obviously it depends on the computers. For example, let's say 1000 calculations per second.
So time in seconds = 2^1000 / 1000 = 1.071509e+298
Then you can convert in minutes by dividing that number by 60, and so on.
The formula is: timeInUnit = nbCombinations / (CombinationsPerUnit * nbComputers)
The time to try all combinations is the number of combinations divided by the number of combinations the computer can do in that time unit, again divided by the number of computers you have.
HOWEVER, to reach a particular sequence, you can, on average, divide that time by 2. Because in a real scenario, you don't have to try every combination, you stop when you get the one you want. On average, you will hit it after having exhausted half the possibilities. You could get lucky and hit it on your first try, or you might have to go through every combination.
Now, to hit a certain number of sequences, say 3, how much time does this take on average? Not three times as much, because at most trying every combination will guarantee you hit those 3. But it has to be more than half the time, right? Well, that's a fun probability problem, I'll let you figure it out.