Anything over 160 characters (80 if you use a language that uses Unicode) has to be sent as multiple texts or as an MMS, since SMS is limited to 140 octets (and 140/7*8=160). Most text apps can be set to not break messages (send them as MMS) or to send long texts as individual texts or some wording that lets you set it for either way. (When we convert from SMS to RCS [which will probably take a few years], that goes away - we'll be able to send texts and files of any size. But all carriers have to agree first, then they have to convert.)