By Sylph.Wardeniii 2012-09-27 12:41:51
In short, like it was stated above -- having all of your subcrafts capped is never a bad idea, unless it is distracting significant time from capitalizing/optimizing your main.
You will be sticking to your main craft for profits, that is why it is your main craft. Generally, any profits that could be made by utilizing a level 70 subcraft will be impractical, because there is some guy out there who has your subcraft in question as his/her main craft -- and can likely do anything you could possibly attempt to do far more efficiently, with more profits, less breaks, etc.
Every craft has its commonly associated set of necessary subcrafts as well; so in that sense, certain subcrafts are not considerd "nice", as they are obligatory. For instance, any serious leatherworker will generally have goldsmithing, clothcraft, and smithing subs all capped to 70, since these are the most common subcrafts utilized for any leather synths. Wood, bone, and alchemy are faaaar less common subs. Chances have it though, that no matter what main craft you choose, you will have to level at least two or all of the following subs: Smithing, Goldsmithing, Leather, Cloth. A lot of synths require some random ingot/piece of leather/piece of cloth, and as such those crafts are often necessary for any high level armor.
The best way to plan out your path in my opinion is to look at your goal synths: "Why am I choosing to level X craft in the first place?" Examine what those synths require for subcrafts, and if you haven't -- start/continue building guild points immediately for your main craft, since that often cockblocks people and will take a month and a half or two to acquire the smock/+1 skill accessory/Emblem. Moreover, if you have the funding I would strongly suggest you start buying materials for your end goal synths now. It's a crying shame to finally hit your desired main/subcraft skill levels to really start pumping out HQ's to simply be sitting around waiting for items to appear on the AH that only pop up 2-3 times a week.