Year in, year out
Definition 1 of 1
Pro Tip 1/3Unchanging Routine
Expresses something done with such regularity it becomes a fixed part of life, without change. 
He goes jogging at 6 am, year in, year out.
Pro Tip 2/3Not Just Holidays
'Year in, year out' isn't limited to annual events but includes regular occurrences. 
She has attended the book club meetings, year in, year out.
Pro Tip 3/3Emotional Implication
Can imply a sense of monotony or steadfastness depending on the context. 
The couple celebrated their anniversary the same way, year in, year out.