AlfieWhattamMagic:
I think the point that people are trying to get across when they advise magicians to only learn a certain number of effects is that magicians should focus on mastering the performance and presentation of a few effects rather than just learning the secrets to multiple effects. What is important, as Canadamagic and the other posters have said, is the quality of how you perform the effects you know, NOT how many tricks you know the secret but can't perform. I agree that if you want to perform an effect, you should be able to perform it blindfolded (or at least while looking at your audience).
I also agree you should limit the effects in a routine to two or three effects and that if you perform too many unrelated effects that you will lessen the impact on the spectator.
However, I'm not sure I agree with your assertion that short routines are good and long routines are bad, to the extent you are talking about how long the routines take rather than the number of effects. For example, performing three "fast tricks" in three minutes is not an effective routine. In that case, there probably isn't enough patter provided for each effect (which is necessary to build up the impossibility of what you are doing), there isn't a common theme leading from one effect to another and there isn't an escalation of astonishment.
First, the patter... A effect without patter is just a demonstration of slight of hand or a "card trick." Use your patter to make your effect seem more impossible and to establish a connection with your audience.
Second the theme... The theme is the relationship between the effects you are performing. That relationship could be that all the effects involve a reversed card (1 - simple reversed card in deck, 2 - spectator inserts "indifferent" card upside down into deck only to find that the reversed card they inserted is the selected card, 3 - Invisible Deck) or that all the effects demonstrate the principle of "sychronicity" (1 - Do as I Do, 2 - RRTCM's Double Reverse, 3 - RRTCM's Intuition with Cards) or that all the effects play off one spectator in a group's ability to influence the outcome of an effect (1 - Here then There, 2 - RRTCM's Ewephindit, 3 - Rich F.'s Tagged performed by having the spectator try to transmit their thought of word to another spectator and having that word appear on the other spectator's arm). The theme ties the effects together, providing a reason for doing all three of effects together (other than "here is something else I can do."). The theme also helps the audience remember what you did because all three effects are connected in some way.
Finally, the escalation of astonishment. Every effect in a routine should be more astonishing than the effect before it. You start with a more basic effect and become progressively more astonishing. Again, this helps the spectators remember their experience. You can almost here them saying, "The magician did this, then he did that and then, you wouldn't believe what he did for the finale."
All of that takes time to develop and time to perform. So shorter isn't always better. Take your time in presenting your magic. It will make a huge difference in the reactions you get.
Finally, I agree that you shouldn't perform "tricks" off the top of your head, but just performing three unrelated effects in a row doesn't make it a routine. There is more to a routine than that.
So here is my question.... can you turn the Biddle Trick / Card to Mouth / 2 Card Monte and Greed / Clutch into a routine that has effective patter, a common theme and an escalation of astonishment?
One final note, spongeballs generally are a routine (generally having three phases) in and of themselves.