How to pronounce "えい” in words?
Is "えい" pronounced as two vowels "ei" or as one lengthened "e"? Or does it depend on a word? For example, how do you pronounce "えい" in ”生活”?

Question

How to pronounce  "えい” in words?
Is "えい" pronounced as two vowels "ei"  or as one lengthened "e"? Or does it depend on a word? For example, how do you pronounce "えい" in ”生活”?

Answer

Japanese えいsound is not so clear compared to English ei sound.
For example えいが which means movie,
we pronounce like えぇが. 
You should ask native Japanese to pronounce it.

Answer

The 生(sei) in 生活(seikatsu) is the same 生(sei) as in 先生(sensei)

You have heard and said the word 先生(sensei) one hundred million times already.

It is the same...

Answer

>Is "えい" pronounced as two vowels "ei" or as one lengthened "e"?

Either works, but one lengthened "e" is more usual.

You can pronounce えい　in せいかつ　like 　えー（EE）, not えい(EI).

The NHK日本語発音アクセント新辞典 says that ”生活 is pronounced as ’せーかつ（SEEKATSU）’(* NHK in Japan is like BBC in England)

※ And 映画（えいが） is pronounced like "えーが（EEGA）" according to that dictionary.

I said that you "CAN" (not "should" nor "must")

So if you want to, you can pronounce 生活 as SEIKATSU, 計画 as KEIKAKU, not SEEKATSU nor KEEAKKU.

In this video, https://www.youtube.com/watch?v=OP2JRAY3c5I
計画 is pronounced as 'kEIkaku" (at 2:27)