they approximately grow 1 path every 1-2 months sitting still (faster if you eat carrion? But I've never done so, too risky to bring along on the front lines before they mature.)
they start at path 1, and matures fully at path 8, so give or take a year. Grow them at your lowest pop provs (or one with gold sites where you want to bring pop down to 0 anyway), fort a bonus to keep them safe, they eat pop.
They can see battle anywhere around starting around path 6 (or 9-11 months of growing) when they have enough hp/mr and paths to be useful, though that's only 2-3 months away from path 8, I usually wait unless I am in great need of them... they get increase to all stats as they grow, HP, MR, Str ...etc
They are awesome battle mage and SC alike, W4D4 at maturity! I always get a headache debating what role to use them in. Do note they are undead (hence weak to anti-UDSC gear and anti-UD spells. They also have a 50% fire weakness.)
I think the pros and cons are pretty obvious given the details provided
