So you're writing a plain text file. You know about Line Endings. So how many characters should be on a single line of text before you put in a line ending?
There are various answers, but my preference is 78, and here is why.
FROM RFC 5322 - INTERNET MESSAGE FORMAT (2008):
There are two limits that this specification places on the number of characters in a line. Each line of characters MUST be no more than 998 characters, and SHOULD be no more than 78 characters the CRLF.
The 998 character limit is due to limitations in many implementations that send, receive, or store IMF messages which simply cannot handle more than 998 characters on a line. Receiving implementations would do well to handle an arbitrarily large number of characters in a line for robustness sake. However, there are so many implementations that (in compliance with the transport requirements of [RFC5321]) do not accept messages containing more than 1000 characters including the CR and LF per line, it is important for implementations not to create such messages.
The more conservative 78 character recommendation is to accommodate the many implementations of user interfaces that display these messages which may truncate, or disastrously wrap, the display of more than 78 characters per line, in spite of the fact that such implementations are non-conformant to the intent of this specification (and that of [RFC5321] if they actually cause information to be lost). Again, even though this limitation is put on messages, it is incumbent upon implementations that display messages to handle an arbitrarily large number of characters in a line (certainly at least up to the 998 character limit) for the sake