The spells have long casting times: 2 weeks and a month. How much of that time does the sorcerer need to spend casting the spells? All that time without interruptions? Or he spends some time each day through that period, but has time to do other things?
I would go with the standard answer: 8 hours a day spent "casting" the spell and the sorcerer can't do any particularly stressful activity durring the rest of the time (such stressful activities including, but not limited to, combat, travel and item creation).
I agree with Argo that a large portion of the Sorcerer's day should be dedicated to not onlyh the casting but making sure the supply of any material components stays constant (refilling incence and oil burners, choosing the next sacrifice if you have options etc...)
For spells of that magnatude that boast the description Cosmic need the uninteruppted hours of meticulous focus and concentration to achieve. Probably only enough time left to rest and eat.
So the sorcerer is basically out of the picture during that time. This is when feats like sleep mastery probably come handy.
Some more questions:
When will the time or stars be right for the effects of the spell to come into play? When the spell has ben cast (right after the casting time concludes)?
Or will the spell reveal a propper time to the sorcerer? Say the spell reveals that the propper time to attempt this will be during the next new moon or something?
Or does the spell linger until used by the sorcerer?
This could have interesting effect on gameplay and timing. If it is the first case, then a sorcerer should get timely information about his opponent, and the time when he wants to oppose him will be, so he can plan ahead to start casting the spells so they are finished in time to get the benefits. Maybe there wont be enough time to cast the stars are right, but enough to still cast the time is right.
Or if the second. Then the sorcerer will have to somehow force his opponent to act in the time revealed by the spell.
Sorcery casting that takes that long is a major drawback, IMHO.
Preparation time takes time away from other things, so I would opt for "Spell Catering." That way I can tend to my guests, refill drinks, mingle, etc. :lol:
I'd decide that as GM case by case, depending which one is dramatically better. Since CONAN players seem to be older than most RPGers there is a good chance that they are mature enough not to provoke some rule discussions at the table.