Occasionally people discuss creating a limit to the number of slotless tokens that can be brought on an adventure.
I want to put forward an argument here that: such a limit is not necessary, because slotless items are limited by other factors, including:
a. The number of combat rounds in a dungeon.
b. Your mental capacity.
c. Physics.
Of course the conclusions below depend on the effects granted by slotless tokens, so I'll make some recommendations below on that.
First: Slotless tokens are effectively limited by the number of combat rounds in a dungeon.
A large number of slotless tokens only work during combat (Horn of the Valkyrie, Druegar's Death Die), or have effects that are only beneficial during combat (Pouch of Tuz).
You get 3-4 rounds per combat tops, and 3-4 combats per dungeon*. This means you'll get 9 to 16 standard actions, and 9 to 16 free actions. Once you have 16 or so slotless items that only do something interesting in combat, and require some kind of action, you're effectively limited - you can't use them all.
Second: Slotless tokens are limited by a player's mental capacity.
There is a lot going on in the dungeon, without trying to remember 20 conditional, optional effects. Large numbers of slotless tokens reward skilled play, and players who prepare or are quick on their feet.
If you simply hand a bag of 20 slotless tokens to a new player they will get very little use out of them.
Allowing for large numbers of slotless tokens this adds a skill element to TD.
It's hard to keep track of 10 slotless effects. No one can keep track of 100 unless they are all very similar (e.g. -1 to fire, -2 to fire, -3 to fire, -1 to cold, ...).
Third: Slotless tokens are limited by physics.
Tokens are relatively large, heavy and difficult to manipulate in a dark, crowded dungeon. It would be very difficult to physically manage and have on hand to show a DM more than 30 or so tokens - even that I believe is pushing it.
Design Conclusions to Support Unlimited Slotless items
To avoid a scenario where slotless items create power creep that is difficult to balance, around, we can follow these principles:
1. Slotless items that effect the party card should be exceedingly rare, and probably up for reprint every few years.
2. Slotless items that don't require any kind of an action in combat to use should be considered carefully, and probably be rare.
3. Slotless items that require an action in combat to be used are not problematic, their "slot" is effectively a "combat action slot" of which a player gets at most 16.
* Per non-grind dungeon. We shouldn't be balancing tokens or making main dungeon equipping rules to support Grind - Grind is free to make any changes as it sees fit.