One of the things I found is that if you have a hard time leveling alts like I do (I prefer to focus on my main) your gathering skills on your higher level toon are wasted on your lower leveled alt; most of the stuff you gather is used in making things that are beyond the skill abilities of your alt.
I made a Draenei shaman a while ago and selected Engineering/Jewelcrafting as her professions. Having spent some time with 375 skinning on my main in Outland, I grew bored with it and dropped it two days ago and took up mining. Over the last couple of days I've been zipping around lowbie zones mining my butt off (now @ 125) and both smelting ore to send my alt bars and sending my alt unrefined ore to prospect. I'll have my level 11 shammy to 150 in both Jewelcrafting and Engineering in no time with an abundance of ore left over to sell. I like dual-tasking craft skills (using them to level professions on other toons and also for earning gold on my main) but eventually, I'll have to spend some time leveling my Shaman or all of the ore I get is going to either accumulate beyond reason or wind up sold.