Well it’s never a good idea to sell your entire stack but there are times when taking profit is essential. Altcoins still seem to follow the standard four year Bitcoin cycles which most of us are familiar with. Obviously the answer to your question is to sell when you are in profit. To maximise your profits though you should sell some in halving year and one year post halving, specifically the year post halving so that’s next year.
Im not so sure if just selling altcoins a year after Bitcoin's halving is really the best plan. Taking profits at the right time matters, yeah, but the market is more complicated than just Bitcoin's four-year "schedule" and the whole altcoins follow Bitcoins cycle thing might be true in a basic sense, but theres a lot more going on under the surface. Like way more factors impacting prices left and right. So while the halving timeline gives a good high-level view, actually nailing the perfect time to sell involves getting into the weeds a bit more. Maybe rigidly sticking to the sell after a year idea leaves gains on the table. But hey, at the end of the day, do what works for you. The altcoins markets can be tricky to figure out.