Who gets used more (innings)... short relievers or middle relievers?

I have these 4 relievers to plug in as short and middle guys and I want to make sure the ones with the most innings get used more often on the road. Additionally, I want Kim to pitch a lot and I also want him on the mound during important innings.

Byung-Hyun Kim (R) - 7.7 Grade / 5.9 Clutch / 122.1 IP / .661 LOPS / .606 ROPS
Paul Shuey (R) - 6.3 Grade / 6.2 Clutch / 69 IP / .697 LOPS / .634 ROPS

Javier Lopez (L) - 8.0 Grade / 5.6 Clutch / 58.1 IP / .622 LOPS / .720 ROPS
Ron Mahay (L) - 8.6 Grade / 6.1 Clutch / 45.1 IP / .628 LOPS / .605 ROPS

My guess

I'm thinking I should use Kim as a short guy to get him more innings and use Javier Lopez as a short guy because he has more of a platoon split and short guys are used based on matchups.

Thus I think that Paul Shuey and Ron Mahay should be middle guys (basically by default)

Note -- I realize that Kim can start and that I will have to do that sometimes to use all of his innings. But when I put Kim in the rotation then I have to use Millwood or Morris in middle relief. Since that doesn't sound like it makes make sense I want to use Kim out of the pen as much as I can.