I'm all for having a healthy staff before the stretch run, but these guys don't need three days off in a row after throwing an inning for two out of three days.
davis and herrera probably do need to be used sparingly. it's not so much about days off in row as cumulative innings. they pitched a ton last year due to the postseason and they're both on pace to pitch a ton again this year if you include the postseason.
i haven't seen any data rich articles on reliever use, but conventional wisdom seems to be that using them more than 70 innings or so per season is detrimental. in the absence of data, it seems prudent to stick with that as a rule of thumb. since they're likely to throw a lot of post season innings, i'd prefer to see them limited to 65 or less in the regular season. which would mean using them a a fair bit less than they were used in the first part of the season.
not to mention - every time they go out, there is some small chance of an injury. risk management with that in mind would dictate using them no more than is necessary to keep them sharp.
it's kind of a let down after the fun of last season's august and september, but the royals and royals fans this season are really just killing time until october. in a way, it's too bad detroit decided to suck so much this season.