Over at Third Edition House Rules there was a post recently about recalling spells, and I made a comment about my own house spell slots rule. Rather than respond in the comments section, I am posting a bit of info about my house rule here.
The idea is we turn spell casters into spontaneous casters. This was mainly to address two issues in our game. First - to eliminate the time spent in our game selecting spells to take. We don't get to play often enough and I didn't want to consume any more time for player preparation when ever there was spell recharging. Second - to have all those interesting spells that infrequently or never get chosen because unless you have very specific information, you just have to choose certain mainstay spells to be successful. For example, if a low level wizard has to choose between Sleep and Animate Rope, just how often is the latter going to be selected?
I won't post the entire house rule, but I'll summarize bits of it. There remain requirements for resting, a quiet environment, preparation time and high enough ability level to cast the spell. Wizards still require a book.
slot is the capacity to cast any single spell of that level the
spell caster bound during the preparation ritual. The number of spell slots is basically the same as the number of spells a caster can memorize according to the RAW. A spell caster always has the
option to consume a higher-level spell slot with a lower-level spell. So, for example, a Wizard prepares a spell slot and binds spells from her book in ritual preparation for consuming that slot when a spell of the appropriate level is cast. Or simply put, one first level spell slot allows you to cast one first level spell.
We also allow more frequent replenishment than RAW, so there are some recent casting limits to prevent taking advantage of the ability to get spells more often. Unless a spell is permanent, instantaneous or has duration of a full
day or greater, spells that a wizard has cast that are still in
effect impact her available spell slots. A spell slot is connected
to such spells, and if replenished immediately ends or dismisses the
active spell upon the completion of the spell slot replenishment
ritual. A wizard can choose not to replenish one or more individual
spell slots, and therefore keep those spells in effect.
So, in practice, what effect does this have on our game? If does have the desired effect of reducing in game spell selection time, and it has had the desired effect of enabling more frequent use of what would be otherwise less popular spells. It does give spell casters a boost in power, and we have given other classes a few house rule changes to share the love. Using this house rule it is also wise not to make too many Wizard spells available too quickly. As an experience DM, I find that bumping the challenge rating to address this power increase is not any more difficult than managing challenge ratings given a party's overall capability, size, kind of magic wielded, etc.
As always with house rules, your mileage may vary. The dice never lie.