How long does it take to drive 800,000 miles at 55 mph consider 10 min gas/bathroom and two drivers?

-- You haven't told us how many times they stop for 10 minutes.

If they stop 1 time. . . . . .  606.06 days
If they stop 2 times. . . . . . 606.07 days
If they stop 3 times. . . . . . 606.08 days
If they stop 5 times. . . . . . 606.10 days
If they stop 10 times . . . . . 606.13 days
If they stop 50 times . . . . . 606.41 days
If they stop 100 times. . . . . 606.76 days
If they stop 500 times. . . . . 609.53 days
If they stop 1,000 times . . . 613.00 days

-- I don't see yet how the number of drivers makes any difference.

Did you really mean 800,000 miles?  That's like to the moon 3.36 times.