What actually damages a deck
Four things, in rough order of how much harm they do: humidity, which warps cards and makes laminated finishes stick together permanently; direct sunlight, which fades ink noticeably within months on a windowsill; riffle shuffling, which creases the larger tarot format far faster than it does playing cards; and hand oils, which build up on gloss finishes and accelerate wear at the corners.
None of these are exotic. A deck kept in a drawer, shuffled gently, and handled with reasonably clean hands will outlast a deck given elaborate ritual care in a humid bathroom.
Bag, box, or tin
The original tuck box protects the cards and falls apart within a year of daily use, its flap tears first. A drawstring bag in cotton or velvet protects against dust and light and offers no structural protection, so cards bend if the bag gets squashed in a drawer. A rigid tin or wooden box protects against everything except humidity, which it can actually trap.
The practical answer for a deck in daily use is a rigid box with a bag inside it, or simply a sturdy box. For a deck in storage, add a silica gel sachet, which addresses the one thing a box makes worse.
Shuffling without destroying the cards
Riffle shuffling is the fastest way to randomise and the fastest way to crease a tarot deck. If you riffle daily, expect visible edge wear within a year. Overhand shuffling is gentle and slow to randomise, so it needs far more repetitions than most readers give it.
A wash, spreading the cards face down on a table and swirling them, is the best option on both counts: it randomises thoroughly, it is the gentlest of the three on card edges, and it is the only method that reorients cards, which is how reversals get into a deck at all.
Fixing what has already gone wrong
A bent card can often be flattened by placing the deck under a heavy book for a few days, though a hard crease is permanent. Cards stuck together from humidity should be separated slowly from a corner rather than pulled apart; forcing them lifts the laminate and ruins both. Fanning powder, sold for playing cards, restores glide on a deck that has become sticky, and a very small amount goes a long way.
A card that is damaged beyond use is a genuine problem for a 78-card deck, and most publishers will not sell singles. It is one of the better arguments for keeping a cheap second copy of a deck you use every day.
Where ritual fits
Plenty of readers keep their deck wrapped in silk, with a crystal, or in a dedicated box, and none of that is at odds with the practical advice above: silk is a perfectly good dust barrier. The distinction worth drawing is between practices that protect the cards and practices that mark the deck as significant to you.
Both are legitimate and they are not the same thing. Storing a deck on a sunny shelf because it looks right there is a ritual choice that will fade your cards, and it is worth knowing that is the trade you are making.