Most of the times it is not worth the hassle to stash away all enchanted weapons. But there are a few things to consider:
Store away the dangerous brands. Or, toss them into deep water or lava.
Be careful around distortion weapons, and weapons that exploit a natural weakness you have. Such as anti magic weapons as a mage, or orc-slaying as an orc, or even holy wrath weapons when you are undead, or change into undead.
It also depends on the weapons. A dagger of orc slaying is no big threat in a monsters hand as the dagger has low damage. (I don't know if the monsters base damage is also multiplied).
Branded Ranged weapons
It is usually wise to stash or dump ranged branded weaponry. A monster picking up a bow of flame can be a hassle, especially when there are more monsters around.
If you are not immune, always get rid of curare needles.
High end Armor
The only armor I usually stash or get rid of is plate armor or better. A random monster that finds and uses plate armor can be hard to beat using some builds. I usually either dump it in water, or drop it in the previous dungeon level.
A orc warlord in crystal plate mail can really ruin your day.
Good base weapons
Certain good base weapons you don't want to be used against you should also be stashed or dumped. Executioners axes, demon weaponry etc. Basically all the high damage weapons. Just don't waste a lot of time stashing all that gear.
You should not stash away all blue items. Magical plusses are not that influential in the combat system.
- An orc with a +1 dagger hits for max 5 (base orc damage) +4 (dagger) +1 (magical plus) = 10 damage.
- And with a normal dagger it hits for max 9 damage. (If I understand the combat system correctly).
So the weapon only being magical is no reason to stash it.
This highly depends on the artefact. But in most cases you want to stash or dump them. Just it cannot be used against you.
The best stash locations are the places where normal monsters don't usually spawn to pick up your dropped weapons. Places like the lair (level 1 can very very rarely spawn monsters that pick up items. But I still pick that one usually, level 2 is way to far to walk :D ), the temple, or the vestibule into hell. All these places either do not spawn monsters at all, or only spawn monsters that do not use items.
If you just want to get rid of items while you are clearing a new level. Just go up a staircase and dump them on the previous one. Saves a lot of time.
Alternative to stashing magical stuff
Method 1 Just go through the levels faster. Don't spend that much time picking up gear, and stashing them. Just run past it. The less time you spend the less monsters spawn, and the less chance there is of a monster abusing old equipment. Added bonus, the game takes less time, and you get a higher score when you win.
Certain levels it simply is not useful to stash away weapons. The most dangerous time in a new map is always the first time you enter. As the level is then still filled with monsters. Later there are few new spawns that really are a upgraded by picking up random gear. (If a orc priest is dangerous to you, a random better weapon does not make him that much more dangerous).
Method 2 Pick a god that likes sacrifices. The best is Nemelex Xobeh, become the dungeons vacuum cleaner. Sacrifice all that dangerous excess gear.