Depends on the base, but average is around 15-16 days off a month for line-holders. Ranges from 12 on reserve up to about 21 for some lines.

1-5 day trip mix, depends on the base also. There's quite a fair amount of 5 day trips. Blocks of days off aren't really spread too evenly all the time. Some lines have it set up like 1 off, 4 on 3 off, 5 on 2 off, 4 on 11 off...

Sometimes what Bolo said is true. You're likely to have a redeye or two somewhere during the month, and could be a whole trip's worth. But there are certainly better trips and you can go all month without a redeye.