I have a book called "The practice of English grammar." by Izrailevich, Katchalova. It's quite old.
I wonder whether what it says is true and accurate. Is it really true that you use the simple future tense with these designations of time interchangeably with the future continuous tense?
It says in paragraph § 27 that the future continuous tense is sometimes used alongside with the future simple tense with such designations of time as all day long, all day tomorrow, all the time, the whole evening, from five till six, etc.
When the speaker uses the future continuous tense they show an action as a process, but when the speaker uses the future simple tense they just state a fact of doing the action.
Then it shows these examples:
"He will be reading the whole evening." and "He will read the whole evening."
"I shall be preparing for my examination all day tomorrow." and "I shall prepare for my examination all day tomorrow."
"They will be working in the library from three till five." and "They will work in the library from three till five."
Then it says that when an action with such a time designation is one of two or more consecutive actions, then only the future simple is used:
"I'll come home early, I'll rest from five till six, and then I'll work the whole evening."