The "answer" changes from time to time.
Grand Trines, T-Squares, Grand Squares --- there are times, like now, when T-Squares are very common because outer planets are forming hard aspects to each other. When you throw in some personal planets, there can be groupings of major aspects that occur in certain clumps of time. At other times, it seems that very few aspects of any one type occur.
As for asteroids, if one were to use the 70 or 80 of the more "commonly used" ones, then one would have major aspect patterns always present. Indeed, multiple aspect patterns would be likely to occur. Some use only the four classical (first discovered) asteroids --- this cuts down the number of major aspect instances. But for those 70 or 80 often used, bear in mind that these bodies are mostly in the same general orbital space --- meaning that they often hold their same relative positions for extended periods of time. This increases the frequency of major aspect patterns being present. What will you do with ten T-Squares and eight grand trines?
Most astrologers who use asteroids, such as my long-time friend and associate Martha Wescott, use asteroids which are at chart angles, ignoring all others. Dave
