A life of ... what?

The concept of Torah im derech eretz has many meanings and has been put to use in many varied and sometimes surprising contexts. Here is one of them.

In Baruch She’amar al Tefillot Hashanah, R’ Baruch HaLevi Epstein reviews some of the finer points of the Birchat HaChodesh, the prayer recited in synagogue in which we announce and bless each new month. Discussing the phrase יִראַת שָׁמַֽיִם וְיִרְאַת חֵטְא חַיִּים שֶׁיֵּשׁ בָּהֶם (Chayim sheyesh bahem yirat shamayim veyirat chet: “A life which has within it fear of Heaven and fear of sin”), R’ Epstein finds it strange that this phrase comes at the end of a list of things we want for life and which we express in the form of חַיִּים שֶׁל (chayim shel: “A life of…”). Why do we change the formula here from chayim shel to chayim sheyesh bahem (“A life which has within it…”)?

By way of an answer R. Epstein offers a hypothesis. If the prayer had asked for a chayim shel yirat shamayim veyirat chet, it would be requesting a life that was so absorbed in fearing Heaven and fearing sin that there was not a moment left for anything else. However important these human qualities might be, and however dear to God, they must surely be combined with other things if humans are to live a full and meaningful life.

In support of this notion R’ Epstein cites the concept of im ein Torah ein derech eretz, ve’im ein derech eretz ein Torah (“If there is no Torah there is no worldly occupation, and if there is no worldly occupation there is no Torah”: R’ Elazar ben Azariah, Avot 3:21). He then cites the famous argument between Torah purist R’ Shimon bar Yochai and pragmatist R’ Yishmael as to whether a life of Torah learning without derech eretz can be sustained: the Talmud (Berachot 35b) reports that many did as R’ Shimon taught and were unsuccessful, while those who did as R’ Yishmael taught prospered.

I do not know offhand of any other explanations offered for the change of rubric. Can anyone enlighten me?