Is clotting risk after astrazeneca covid-19 vaccine only for a short duration or for a very long period of time (may be for whole life)?

From experience and data so far, the elevated risk probably is gone after about 2 weeks. But after that, stay tuned to news reports on it, to be on the safe side.

These are very rare events and typically occur within 2-3 weeks post JAB. There is absolutely no evidence of any permanent or chronic effects beyond that time. Would not worry

I would doubt for your whole life, but this is a newer vaccine and we have not had it long enough to get long-term data on things like side effects or adverse effects.