It is, and I think "faith" in this sense is indeed an intellectual virtue. But it seems to me that

• many, many uses of the word "faith" by believers are describing something quite different and are in fact endorsing belief in the absence of evidence or in the teeth of contrary evidence;
• even when the meaning is broadly in line with CSL's here, most applications of it refer not to holding on to belief merely "in spite of your changing moods" but advocate much firmer persistence than that. A Christian who after lengthy consideration is beginning to think that the problem of evil is insoluble is likely to be enjoined to exercise "faith".

The second of those is not necessarily unreasonable. E.g., if you know you are about to talk to someone supernaturally persuasive, able to come up with extremely convincing arguments for any position true or false, you might do well to precommit to not being moved by whatever arguments they might offer you. Christians might suggest (indeed, in another place Lewis does suggest) that the influence of the devil is like that. But the possibilities for abuse are very obvious.

[EDITED to add: I see that at least two people have downvoted this. Rereading it, it still looks perfectly reasonable to me. I don't suppose anyone who dislikes it would do me the favour of saying why?]