Single-Minded for Mages : Lengthy spellcasting?

[Plane]

B260 lists Single-Minded among several 5-point advantages selectable by the Mage template

B85 says that's a bonus to "lengthy mental task you concentrate on to the
exclusion of other activities"

In trying to discern what "lengthy" might mean I did a search and found on B244 under the Spasm spell:

If the subject is in the middle of a lengthy spell requiring gestures, he must make a DX roll or start over.

I thought perhaps that might mean any task taking more than 1 second (presumably you could use Spasm to interrupt anything except a 1-second spell since it goes off immediately as of 4E) but then I found this on B202 under interrogation:

+2 for a lengthy interrogation (over two hours);

2+ hours is longer than 2+ seconds...

and then B22 mentions "a lengthy period of re-education (see Chapter 9)" in respect to buying off a low TL disadvantage (-5 per level) which I expect refers to B292's "Improvement Through Study" rules. 200 hours of learning per point would mean 1000 hours to buy off one level of Low TL...

120+ days is longer than 2+ hours...

So there might not actually be a clear idea of what "lengthy" is, allowing wiggle room for GM to figure out, or perhaps this got clarified later?

This would also be important for knowing how to apply the Autohypnosis skill as B279's option "Improve Concentration" only applies to a "lengthy mental task". Same with B163's "Attentive" quirk.

If a minimum of 2 hours were required, even Ceremonial Magic (10x time) probably wouldn't go that long... even with another x2 (x20 total) to get a +1 bonus (one of the optional rules). Unless it's possible for a mage to intentionally take longer to cast a spell for the purpose of getting a bonus from SM/A/AH:IC

If that is possible, the Continuous Ritual perk (T:MSp23) should be taken into account. It allows you to have a spell ready and hold it indefinitely until you're ready to set it off, so a house rule should be more limited in that if you commit to a certain "finish time" you should have to stick with that (can't set it off earlier, can't set it off later)

[whswhs]

My ruling, for my own fantasy campaign, was that ritual magic (in my case, Path and Book magic) takes long enough to get the Single-Minded bonus. But if you used the rule that lets you perform a ritual in less than a minute, in an emergency, at a penalty, no Single-Minded bonus for you; that short a time isn't long enough to need single-mindedness.

In general, a short P&B ritual is 10 or 15 minutes.

[Prince Charon]

As for standard magic, I suggest that ceremonial magic is easily long enough, so if you're playing an enchanter, or someone else who uses ceremonial magic a lot, it's a pretty useful advantage. Likewise if you're an alchemist.