No flashpoints are limited time. You can do them anytime after you get them, even soloing them later. Tython has no P. And you could do warzones if you want some xp, they can be fun.
Also bias, but I say try out the non-Forcie classes. I like Trooper and Agent, but BH and Smuggler are good too I hear.
"Sir,we are beginning our search for these rumored 'underwater villages'.They will not stay hidden for long". -Battle Droid Commander OOM-9!