て以来・
て以来 sets a past starting point and says that a state, habit, or absence has continued from then to the present or another reference time. てこのかた expresses the same basic span more emphatically, usually suggesting that it has been substantial.
What must continue
The first part identifies a completed event or past period as the starting point. The second part must cover the interval after that point: it may describe an ongoing state, something that happens repeatedly, or something that has consistently not happened.
States, habits, and continuing absence
新しい薬を飲み始めて以来、体調は安定している。
My condition has been stable ever since I started taking the new medicine.
Analyze子どもが生まれて以来、毎晩寝る前に日記をつけている。
Ever since my child was born, I have kept a diary every night before bed.
Analyze卒業して以来、彼とは一度も会っていない。
I have not seen him once since graduating.
Analyze入社以来、同じ研究チームで働いている。
I have worked on the same research team since joining the company.
AnalyzeNeutral versus emphatic
Both versions describe the same continuing support. The first presents the time relationship neutrally; the second gives the thirty-year span more emotional or reflective weight.
三十年前にこの町へ移って以来、近所の人たちに支えられてきた。
Ever since moving to this town thirty years ago, I have been supported by my neighbors.
AnalyzeNeutral and suitable in ordinary speech or writing.
三十年前にこの町へ移ってこのかた、近所の人たちに支えられてきた。
Throughout all the thirty years since moving to this town, I have been supported by my neighbors.
AnalyzeMore reflective and emphatic, with attention on the long span.
Choosing among nearby expressions
て以来 neutrally establishes an interval continuing from a past point. Simple てから can merely place one event after another. てからというもの gives greater prominence to a striking change after the first event and often carries a stronger personal evaluation. たきり more readily suggests that an expected return, repetition, or next step never occurred.
More examples
父が退職して以来、朝は二人で散歩している。
Ever since my father retired, the two of us have taken walks in the morning.
Analyze震災以来、この地域では毎年防災訓練が行われている。
Since the earthquake, disaster-preparedness drills have been held in this area every year.
Analyzeあの議論以来、彼女とは連絡を取っていない。
I have not been in contact with her since that argument.
Analyze研究を始めて以来、この疑問がずっと頭から離れない。
Ever since beginning this research, I have been unable to get this question out of my mind.
Analyzeこの店は開店以来、地域の人々に親しまれている。
This shop has been popular with local people ever since it opened.
Analyze先月このかた、まとまった雨が一度も降っていない。
Not one substantial rainfall has occurred since last month.
Analyzeその旅行まで、生まれてこのかた海を見たことがなかった。
Until that trip, I had never seen the sea in my life.
Analyze