Lets break this question down into parts, then you decide.

The lane tells you where to play. If you know the length of the oil pattern and subtract 31, you get the best spot for where you want your ball to exit the oil. For the pattern you are on, this will give you the most forgiveness.

Most straighter bowlers need entry angle to strike (though i seriously question this :)) so they will push that forgiveness area to the outside as much as they can. It would give the illusion they are playing the same line always when that may not be the case. Remember, just because they are hitting second arrow doesn't mean their ball is breaking at 10 board always. They are moving their breakpoint around a few boards and using their arsonal smartly. For shorter patterns, they are getting out towards the gutter a few boards more and for longer patterns they are keeping it a little tighter a few boards EVEN THOUGH THEY MAY STILL BE HITTING THE SAME SPOT AT THE ARROWS.

For a THS, the pattern will be +/- a couple feet at the most and probably very likely the same distance every week. This is where knowing your equipment gives you an advantage. Kegel White pattern is 40 feet so you are now thinking i have to exit at 9 board. One problem though, after the first few feet, outside 9 board is DRY.

So, you pull out your new solid reactive ball and decide to play straight up 9 board. If you miss outside (towards the gutter) your ball hooks up on the dry lane and by the time it gets down the lane it is dead, no hook left, all its energy is spent. Or, you decide to move in a little and play 11 board out to 9, keeping the ball in the oil trying to reserve the balls energy for downlane hook. But, you just can't quite get the ball to make it back to the pocket for strikes. Hmm, what to do now? What ball are you using again? Oh yeah, a new solid reactive ball. And it won't play inside, even a little bit? Go back outside and pull out a ball that isn't so strong (cover wise), like a 4000 grit polished pearl. Now, do the same thing you just did with the solid reactive. What did that do? Maybe need to take the polish off of it and go just with the 4000. Try it again. It's nice when you have them already prepped and ready to go, just grab it out of the bag and bowl. Not always possible, sometimes they throw one heck of a curveball at ya (like out of bounds).

On a THS that you'll see in leagues, i'm not a big fan of mixing up your layouts for how you have your balls drilled. In some cases, yes, not for most it's just not needed. Find the reaction you like in a ball and change cover strengths. The more inside you like to play, the stronger your grits could be but an outside line bowler would best be served staying high in the grits, no more than 2500-3000 at the lowest.

There is no oil made that won't breakdown on you, sooner or later you will need to adjust. Maybe you can go all three games or maybe not, but knowing your baseline ball dynamics will serve you well when making that move.