I've been using VoiceAttack for several years now, and my "General Desktop" profile has increased in its size considerably, now hosting several hundreds of (voice-activated) commands, some of them also multi-segmented. I presume that a large number of commands in a profile (whatever that "large" number would be) may alone cause VoiceAttack to operate sub-optimally.
Does it help to split one large profile into two or several smaller ones, to increase the app's overall performance (or: the accuracy of voice recognition)?