An allowance you skip does not roll over.
01
The Rs 125000 is per year, not per lifetime. It resets every April and does not carry forward. Skip a year and that slice of tax free room is gone for good.
02
Never selling is a fine instinct with one blind spot. It keeps you invested. It also stacks every rupee of gain into one lump at the end, taxed almost fully at 12.5 percent, because a single year of allowance barely dents twenty years of gains.
03
Harvesting is just realise, then rebuy. Sell enough long held units to book about Rs 125000 of gain, pay nothing on it, buy the same units back at the higher cost. Two honest catches. The rebought units start a fresh twelve month clock, and small costs apply, so it suits holdings you were never going to trade anyway.
The market decides your return. The tax code quietly hands Rs 125000 of it back every year, if you reach for it. Most people never do, and call the forgetting discipline.