In light of the highly regular pluralization in English, compound phrases are instinctively pluralized by likewise adding an s. For example, a parent might say to a child, "I'm really sick of hearing your constant I-didn't-do-its!" I have seen this sort of hyphenated compound construction in German in the translations of the Harry Potter books; e.g., du-weißt-schon-wer for you-know-who. But this is, of course, singular. Given the irregularity of German pluralization, how, in general are similar compounds made plural?
I would do it just the same way as in english: pluralize the last part of the compound:
Ich habe genug von deinen "Ich-wars-nicht"s!
But i actually never hear it. Germans do not use such constructions too often. Instead, a paraphrase is used:
Ich habe genug von deinen Ausreden!
I don't think there is one way, that will always work, but let me suggest how I would translate your example using a compound:
Ich habe genug von deinen dauernden Ich-war-es-nicht.
Compare it to
Ich habe genug von deinem dauernden Ich-war-es-nicht.
deinen shows the following is plural, while deinem shows singular. This works here, but could fail for other hyphenated compunds.
As @marstato said, Germans would probably use a paraphrase here.
I think that such phrases with hyphens are used seldom. The thing I just remember is: Hanns Guck-in-die-Luft (Struwwelpeter), but then it is a replacement for a name and not a quotation used as a noun. I would write it just with quotes and without hyphens:
Ich habe genug von deinem ständigen "Ich war es nicht".
In this case I would prefer singular.