Non-permanent magical armor or weapons

Magical items typically take one of three forms -
1) Single-use (potions, scrolls)
2) "Charged" (wands)
3) Permanently enchanted (Armor/weapons)

The creator's required level, skills, cost, and time is is likewise increased through the three categories.

Enchanted armors and weapons are typically considered to have permanent bonuses/abilities unless acted upon by a sufficiently powerful magic (dispelling, curse, etc.)

However, could there be scenarios for non-permanent enchanted weapons/armor, either by fault or design?  I'm thinking of a few possibilities:

1) Faulty enchantment - low percentage chance of failure, object not "taking" powers and they fade over time (days to years), decreased bonuses perhaps - +2...+1...+0...  Enchantment decreases on critical hit or fail (magic fades out - vs non-bonused magical item).  Someone else recently discussed armor repair costs, including a proposal for repair to magical armor - since it can be damaged - there is the potential for magical degradation (half-life?) as well.  Likewise, the enchantment could be a sham, with the duped character using an enchanted item that fades to normal after a set period of time (most likely at a MOST inopportune time)...

source

2) Purposefully temporary - For instance for a battle or a single event. This could be a stronger version of a temporary spell, like enchantments made by an Arcane Archer, or perhaps a degraded version of a spell like Enchant Item.  The spell/limited enchantment would require less cost/components than its permanent version. This could also be used to spread the magical "resource" among multiple recipients/users (e.g. honor guards).  It would definitely have an expiration date.

Hmm.
Enchant Item, Temporary..

Spell Level: Magic-User, 5th Level

Range: Touch

Duration: Months x caster level.

This spell is used in the temporary creation of a magical item, in addition to whatever research, special ingredients, or other efforts the Referee may determine are necessary for the task.... costs will be proportionally less than those required for a permanent enchantment... At the end of the enchantment, the item will return to a mundane state.

Enchant Multiple Items, Temporary..

Spell Level: Magic-User, 6th Level

Range: Touch

Duration:  Weeks x caster level.

This spell is used in the temporary creation of multiple magical items up to a number equal to the caster's level (for instance suits of armor, swords). The items must be identical in nature and construction.  Spell requires whatever research, special ingredients, or other efforts the Referee may determine are necessary for the task.... At the end of the enchantment, the items will return to a mundane state.

(One good point for Pathfinder/3.5 is that the system documents do outline magical item creation costs and requirements. Rob Conley has also put together a helpful resource for S&W.)

3) Damage to object - as I mentioned above - if magical armor/weapons need maintenance - could their enchantments also somehow degrade?
Examples/ideas:
Damage from absorbing spell effects or magical weapon attacks
Powers 'spent' with magical attacks to foes (ex. lycans, powerful undead, other foes that require magical weapons to hit)
'Leakages of magic into targets, yielding benefit to the target..
This degradation would be treated as equivalent of dulling/breaking/other attrition.
Part of enchantment 'worn off ' or absorbed into foes.

If this limitation is known by the character/player - then the magical item will be treated as resource (see 1,2 above) - the player chooses when or how to use it, or is under time-pressure to complete the task/quest before the magic runs out.
Of course, if the magic 'failure' is an unknown effect - a sudden failure or ineffectiveness will create an interesting or stressful scenario ...

Just ideas rattling around in the mind...