SFK drops will last you unitl SM (~10 levels)
SM drops will last you until 50 (10 - 15 levels)
ST Drops will last you until Outlands quest gear (~8 levels)

But that depends on how fast you want to get into outlands. Sit back and enjoy the ride to 70 or go balls out and hit 70? Your choice. :)
I think I replaced some BFD (yes BFD, not BRD) pant with an outlands quest item :) Basically I farmed instances till I got bored, that was based on the XP/drops/annoyance (RFD has amazing caster drops but fast spawning pats ftl)

The girls had all dinged 20 during the run and the quest turn ins got them all up to 21. Now for the lvl 20 class quests for the shammy and the lock...
Ah, and I thought just doing the shaman ones were bad.

My next set will probably be 2 locks and 2 mages paired with a pally I already have, wipe recover + ports + water for minimal downtime :)