〜というもの
for the whole (period), all through
Period (この / ここ + time) + というもの
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というもの after a length of time stresses that something continued for that entire period, and the period feels long: この一週間というもの、ほとんど寝ていない, "I've barely slept this whole week".
The time phrase usually starts with この or ここ ("these past"), and the second half is an unusual continuing state: not sleeping, constant rain, non-stop work.
It's closely related to てからというもの (N2), "ever since", which starts from an event. というもの after a period just stresses its length.
Don't confuse it with というものだ (N2), "that's what … is", or というのは (N3), which defines a word.
Examples
この一週間というもの、ほとんど寝ていない。
I've barely slept this whole week.
ここ数年というもの、休みを取っていない。
I haven't taken a holiday in all these years.
この三日間というもの、雨が降り続いている。
It's been raining non-stop for the past three days.
子犬が来てからの一か月というもの、家の中がにぎやかだ。
The whole month since the puppy arrived, the house has been lively.
この十年というもの、彼女は母の介護を続けてきた。
For ten long years, she has been caring for her mother.