Can I keep a weekday vrat for life instead of a fixed number of weeks?

yes; many people keep a weekly vrat as a lifelong discipline, and then no udyāpana is needed until they choose to stop.

A vrata can be taken in two ways. A kāmya vrata is kept for a set count, often with a wish in mind, and is closed with an udyāpana. A nitya-style vrata is simply a regular discipline, like a grandmother who has kept every Monday for forty years. If your saṅkalpa was “I will keep Mondays as my devotion”, there is no count to finish.

If you later need to stop because of age or health, do a simple closing: a pūjā, a small dāna and a prayer of gratitude and forgiveness. Many elders reduce rather than stop, for example from a full fast to one light meal.

It is also fine to begin with a fixed count, complete its udyāpana, and then continue as a lifelong habit. What matters is that you are honest with yourself about what you promised.

Kāmya (wish-based) vs regular (nitya-style) vrata · Source: common family practice

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