There's no right answer here.

My paladin and mage have an epic flier.

My priest, shaman, and warlock only have the loaner so can't even fly in many zones.

My paladin is my gatherer (herbs/ores) and with crusader's aura its AWESOME. My mage is my current "main" for solo play. His epic flier is also AWESOME.

My other three toons are my Heroics group fillers and professionals (enchanting, tailoring, etc.).

I have all my toons hearthed to the Argent Tourney grounds. I hate dailies too but recently started to need gold. So, I do all the Argent Tourney dailies (not the goblin ones though) on the pally/mage and just the 2 jousting and 2 (nice double dip!) "kill scourge" with my 3. So, it works out to 24 dailies done in a few minutes. If that gets me someday to an extra 5k, I'll get another flier for my 3 laggards. Otherwise, the planned 150% fliers will be great for me and enough to consider taking my other 3 around Icecrown!

Net-net is my 3 non epic fliers..... don't fly much. I also don't feel the need for a ton of gold. So why get them epic'd now?