どき vs じ when using 〜時 as suffix

Question

I'm trying to figure out exactly when to read 時 as 〜どき or 〜じ, when used as a suffix, as in for example 空腹時, 食事時, as well as this sentence from a game I'm playing:

タウンメンバーの加入時に最大HP+20%

大辞林 defines とき（どき） as

（８）（「どき」の形で）名詞や動詞の連用形の下に付いて，それにふさわしい，それの盛んな，あるいはそういう状態の時間であることを表す。（ア）時刻。時間帯。「昼飯―」「会社の引け―」「たそがれ―」（イ）時節。季節。「花見―」「木(コ)の芽―」「梅雨(ツユ)―」（ウ）時機。機会。「書き入れ―」「売り―」「引き上げ―」

and defines じ as

■二■ （接尾） （１）名詞に付いて，「とき」「おり」などの意を表す。「空腹―」「革命―」「第二次世界大戦―」

But it seems like じ just refers back to とき. Is there a specific one you should use for each word, or can you use both 〜どき and 〜じ for a single word depending on the context?

Answer 1

As a general rule, it is pronounced じ after an on’yomi word and とき after a kun’yomi word. However, there are exceptions, and [食事時]{しょくじどき} is one of them.

Curiously, 食事, despite being an on’yomi word, also exceptionally tends to take the politeness prefix お, rather than ご. I cannot explain why. I guess you should memorize each exception.

Answer 2

When the previous word is Hiragana, it tends to pronounce 'toki' or 'doki', while the previous word is Kanji or followed by Kanji, it tends to 'ji'. The exceptions like 「昼飯―」花見―」「木(コ)の芽―」「梅雨(ツユ)―」are the general time for everyone like launch, dinner, or season, not the time only for the person who is speaking or the related people for the speaker. These are almost idiomatic expressions.
It is my feeling as a Japanese.