I'm playing SRO since Easter '06 and I can tell you that I play for fun (it's not a freaking job). So I'd
suggest doing as I did and do not SP farm at lvl 16, but leave a 5-6 mastery/lvl gap and level up. You'll get plenty of sp points on the way (do all the quests) and you won't be stuck at lvl 16 doing the same thing over and over and over and over... (you get the idea

)