Suggaji, Please drop the 'ji' and revert to 'Krishna', otherwise I will feel too important to answer you. 
The puncture thus patched lasts long. I am running two tyres with one patch each at 50 PSI for the last year, and I see almost no pressure loss.
If you are seeing a pressure loss of 5-7 PSI, there is an issue with the tyre (a slow leaking puncture still not detected). Get it checked.
Wheel balancing rotation and alignment should be done at 6 month interval, or better still each quarter. It takes about 300/- here in Noida for all of this to be done at a tyre shoppe.
Puncture in sidewall is generally not considered safe. This is because the sidewall flexes with each turn of the wheel, and there is a possibility that the patch may fail. If this happens in the middle a trip, and the car is moving fast, you may have a roll-over or some other catastrophic accident.
However, if the puncture is patchable (the puncturewalla has the last word), patch it, keep the tyre as a spare, and exclude it from the rotation schedule. I would just curse my luck and replace the tyre.
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