I am not a fan of endgame "epic" non-sense. If I want to try a different class or class combo and do not have a character slot then I will TR and existing character.
Some characters I have a plan for. Some are just for trying new things. Like "Returning" First Life 12Rogue TA/8Monk Human Staff user, Second Life 19Rogue/1Monk Horc UA Assassin, This life he's Helf pure Artificer and coincidentally also my Main crafter.
Mokune is my planned "Completionist"
Thaumat was a Pre-Savant Sorc and I didn't like kiting in ToD with him so I TRd into a Helf PM Wizard
Drow Str Based Rogue is fun to play but would rather be a Helf Str based Rogue or Dark Monk/Rogue Mix
Drow Cleric is a great healer but not tough enough for my play style so, once I get 20 HoX completions and a possilbe Lorrik's Shield he will get TRd
Drow FVS may never get a TR one day but would more than likely TR Thaumat into a FVS at some future time.
The list goes on..
TR gives you the opportunity to play your geared loved toons again and they become a little more powerfull each time.
I suppose I could stick around at 20 and pound my head with big Epic brick but OMG *Ouch*