House Rule: Spontaneous Magic - Daily Uses

Spontaneous Magic – Daily Uses
[Unearthed Arcana pg. 151-152]

• A hero who selects any given metamagic feat gains three daily uses of that feat, and can opt to use that feat “on the fly” without previous preparation, increased spell level, or extended casting time. In effect, the use of metamagic feats come to be very much like the use of metamagic rods.
  
• The maximum level of spell to which the caster can apply a metamagic feat is equal to the maximum spell level he is capable of casting, minus the spell level adjustments of the metamagic feat.
  
• A caster can apply more than one metamagic feat to a spell, so long as he can still cast that spell per the above guidelines.
  
• Each time a hero selects a metamagic feat, he gains three uses of that feat per day, cumulative.
  

Insight: Normal casters have to prepare their metamagic feats in advance, which leads to higher level spells being dropped for the reason of others – for an adventuring company, this means access to fewer high-level spells in a day – increasing downtime. It also means that heroes will likely be forced to cast e.g. silenced spells in combat, or enlarged versions in cramped quarters, effectively negating the effect of the metamagic feat. While spontaneous caster have an advantage here, by being able to choose on the fly, increasing casting times to a full round, offsets that advantage completely, and makes metamagic spells rather useless in combat.
This rules variant will allow all casters to employ metamagic feats much more. It may seem like the heroes have gained significant power, but the limit of daily uses keeps this ability from getting out of hand. And the simple fact that the hero had to expend a feat slot to gain the ability in the first place is still a balancing factor. Plus, of course, the bad guys will have access to the same power.