Yosef Karo

“ According to this, it is necessary to take care not to elongate the shevarim to the length of three terumitin, lest it exit the category of shevarim to tekiah. Some say not to worry about elongating the shevarim a bit as long as it is not too long, and that is how we practice (Mordechai and Hagahot Asheri chapter 19) . The tekiah of tekiah-shevarim-teruah-tekiah should be longer than that of tekiah-shevarim-tekiah and that of tekiah-shevarim-tekiah should be longer than that of tekiah-teruah-tekiah. However, if one elongates each tekiah, there is no problem, as it has no maximal limit. ”