We (read: the GM) had created Lenghtening in our SR3 campaign many years ago after reading Robert Jordans "Wheel of Time" series of books. Here it is converted to SR4. Sorry if anyone has posted something like this.

Lengthening was created to simulate the way Jordans channelers could "tie off" their weave (spell) letting it sustain itself before evaporating. With that feel free to offer suggestions or shoot holes in it.

Lengthening
Lengthening allows a spellcaster to have a spell sustain itself for short periods of time. (Yea, I could describe it better but...)
Spend a complex action and make a Ritual Sorcery + Magic test. (-2 for sustaining)
The number of hits generated X Magic = the number of combat turns the spell is sustained. The caster can use less hits if desired.
Make a drain test equal to 1/2 the force of the spell + the hits use to sustain the spell.
A caster can retake control of his spell but doing so would incur a drain test equal to casting the spell again.
lengthening can only be used on spells that are sustained or permenent. (detection, health, ect) So no lengthening powerbolt or something.

A character can use legthening as a specialization for ritual spellcasting. (gaining +2 dice to legthening)

A mechanic I'd prefer would be to only let it be sustained for Initiate Grade or maybe IG + Magic combat turns. Less dice rolling and less time for a power that gives you the effect of an expensive bound spirit for no nuyen and neglible time preparation cost.

it also sticks with the theme of metamagic abilities being pretty much based off your initiate grade, Slithery.

i agree with the initiate grade method. maybe initiate grade +1 if you are really determined to allow non-initiates to use the technique as well.

I'm sorry, but when I saw this thread title all I could think of was...

Talisman Geas: Little Blue Pill.

Makes me wonder why did they remove the ability to use successes on a ritual spellcasting to sustain the spell?

Back in SR3 you could ritual cast and you could use some of the successes on the spellcasting test to automagically sustain the spell, at a rate of 1 hour per success.

I always thought that was great fluff, I could imagine a group of shaman ritualizing around a campfire and then sending their target off with a 4-6 hour buff to go on his quest with...