According to
Thief Training Reference - MapleWiki.
Hermit Leveling AreasYou may want to consult these sections based on what skill you chose to max first. (Main Attack Skill-wise) Wolf Spiders are good training for levels 70 - 85
Shadow Partner FirstExp Areas70~85 Haunted House (Voodoos)
70~85 Sanctuary Entrance II-IV (Tauromacis / Cold Eyes / Taurospear)
77~85 Ice Valley II (Yeti & Pepe / Yeti)
80~90 Forgotten Path Of Time<3> (Death Teddy)
80~90 Dangerous Cliff (Dark Yeti / Dark Jr. Yeti / Dark Yeti & Pepe)
88~100 Warped Path of Time <4> (Spirit Viking)
90~110 Unbalanced Time (Dual Ghost Pirates)
95~110 Lost Time (Master Death Teddy)
95~120 Forbidden Time (Grim Phantom Watch)
Money Areas80~100 Cave Of Trial II-III (Cerebes / Bain)
Rare Drops88~100 Warped Path of Time <4> (Spirit Viking)
Rare Drops95~110 Forgotten Path Of Time<4> (Phantom Watch)
Party Map Don't bother soloingAll Around Areas70~79 Forest of Dead Trees I-IV (Coolie Zombie)
70~80 Watch Out for Icy Path I (Jr. Yeti)
100~120 Twisted Time (Gigantic Spirit Viking)
Avenger FirstExp Areas70~85 Warped Path Of Time<1> (Buffy / Lazy Buffy)
70~85 Sanctuary Entrance II-IV (Tauromacis / Cold Eyes / Taurospear)
88~100 Warped Path of Time <4> (Spirit Viking)
90~110 Unbalanced Time (Dual Ghost Pirates)
95~110 Lost Time (Master Death Teddy)
95~120 Forbidden Time (Grim Phantom Watch)
Money Areas70~120 Cursed Sanctuary (Jr. Balrog)
Rare Drops; Boss Monster spawn at large time intervals90~110 Unbalanced Time (Dual Ghost Pirates)
95~110 Forgotten Path Of Time<4> (Phantom Watch)
Party Map- Don't Bother Going SoloAll Around Areas
70~79 Forest of Dead Trees I-IV (Coolie Zombie)
73~80 Watch Out for Icy Path I (Jr. Yeti)
73~80 Watch Out For Icy Path II (Jr. Yeti /Jr. Yeti (Transformed) / Hector)
70~80 The Forest Of Gollem (Mixed Gollem)
100~120 Twisted Time (Gigantic Spirit Viking)