There is a time for everything. For example, the time to eat pie is always.
Not everything is like pie. Take coming and going. They are as unlike pie as mice are unlike elephants.
Living abroad, even with the occasional break, is like living in perpetual mental ward. Life can be very, very good-- there is something about being abroad in and of itself that is like happy gas-- but you still are in another universe where the dots do not quite connect. These are not always specific things. Sometimes it's just a longing for x to be like it is back home.
Scientists have developed a word to describe this complex relationship. It's called homesickness. Most people feel homesick within the first six months of leaving their country of origin. I did not. I did not feel it the first year or the second. At of this has to do with my lack of family relations in the states. But starting with my third year, homesickness slowly took up residence. I didn't even know it was there in the beginning.
There is a time to stay and a time to go. It's hard to know exactly when that time is, but if fear is your biggest obstacle, then the time is now. I am terrified of returning to the United States and the depressed job market that sent me abroad in the first place. But I am so very happy to be going home, a place where there are 500 kinds of cereal even though I only usually buy Raisin Brain and Oat Meal. Mostly, I just want to be confounded by choice.