How long a technical indicators support?

Suppose I buy a stock based on technical analysis seeing monthly chart. The indicator has said bullish trend.
Now, how long this trend can remain valid according to technical analysis?

Simple answer is it works till it doesn’t.
There is no guarantee it has to work till particular time or anything etc.
Can check this by nithin on technical analysis.

Thanks, @siva for your reply.

Now, I have solved all these technical analysis problems.
I understood that technical analysis is bogus. The only thing that works is momentum. That I see on price. This also does not guarantee, even chance of being correct is not very high but I try to guess.
For small caps and microcaps, this price movement is also very jerky but whatever is there it is this only to guess.
I have said, Bye Bye to TA after a short stint.

If you are into trading, you will have to do the technical analysis frequently which means that if a trend gets over you get to know about it immediately and then you decide whether to buy it or sell it. This is how analysis works and should be done.