( I read Vishese, a bit, so allow me...)

Originally Posted by
Vish
...You always carry at 18, so last two levels are lost...
So, whether or not you are planning to go on to Epics and Level 30*, most players never take Level 19.** Instead, they park at Level 18 for a while and "bank" the XP for both 19 and 20, and when they hit cap the go straight to 20, get what they need to TR, and reincarnate back to Level 1, good to go.
(* I, personally, do NOT recommend that any new player go on to Epics on their 1st character. Too much to learn, on all fronts. TR once, get a 34 point build, re-do Heroics, learn (and fix) the mistakes you made first time, then decide. ymmv.)
(** Why? B/c if you take Level 19, you miss out on most Level 16 LFM's. A group loses the (+50%!) "Bravery Bonus" to XP if there is a character more than +2 Levels over the base level of the quest. So, a Level 18 character can join Level 16-20 quests, but a Level 19 character can only join 17-20. Not a law, just a common rule.)
So, Vish's excellent point is that, if you are planning to TR at 20, you should plan for an 18-level build, since you'll be at 18 for a while, but might only see 20 for a dozen or two quests (and less if people are helping you farm Tokens).